There are five stages in the Multi Jet Fusion printing process
Jetting into a new dimension
There are times when new technology takes roots and major players in the industry have products that push new boundaries. One such product is the Jet Fusion 4200 3D printer from print giant, HP.
Obviously known for two dimensional printers, it is no real surprise now that 3D printing is a fully fledged industrial process, a company like HP joins the fray with typically high specification equipment.
Just as a background, 3D printing is one of a number of new technologies which is covered by the umbrella term, Additive Manufacture (AM). The premise of AM is a polar difference from typical manufacturing processes where you remove material to produce the desired component; with AM you actually add material (hence the process title) and as such you have no waste.
There are a number of AM processes which use different techniques and materials and it is important to know the limitations of each. Selective Laser Sintering, Direct Metal Laser Sintering and Selective Laser Melting (SLM) are all types of AM that are typically used for metals and components that are needed to be durable and subject to loading. But if you want a cheaper and quicker outcome of an AM process, then 3D Printing is the process needed.
Whilst there are a number of different types of 3D printing under the AM umbrella, HP has developed a new process and equipment that has taken the ability to produce 3D components to both a new level of quality and far greater production speed. This is called HP Multi Jet Fusion Technology.
The hardware consists of a 3D printer, build unit and processing station
Most 3D printing equipment uses the injection of a material so the shape is built up layer by layer with the application head moving upwards, or for more complex shapes the printer applies a layer of material and/or packing (should hollow section be required) and the whole work area drops away ready for the next layer to be applied. This is the case with the HP Jet Fusion 4200.
That description is as basic for 3D printing as saying ‘you put wet ink on paper’ would be a description for traditional 2D printing. HP makes the claim its device can print up to ten times quicker than an equivalent machine with greater definition of edges and profiles. The reason it makes the claim is largely down to the way the paper thin layers are laid down, time and time again.
The components
There are three key components to the Multi Jet Fusion printing process; base material, fusing and detailing agent. The sequence of events to apply just one layer of the desired parts is broken down into five stages.
The base material is laid down across the work space by an application bar passing from the back of the printer to the front and back again. The second stage comprises of heat being applied to this material, followed by a fusing agent, the fourth being a detailing agent and finally a further heating process which fuses the carefully laid down pattern.
The final four stages are completed by a second applicator bar which passes from right to left and then back again in much the same as the material applicator. This second applicator bar contains the heating units and inkjet heads which uses proven HP technology, laying down the aforementioned fusing and detailing agents.
The clever aspect of the Multi Jet Fusion printing process is the combination of fusing and detailing agent. The purpose of the fusing agent is to complete the homogenous combining of the base material when the heat is applied. The detailing material is applied in selected areas to control the fusing action; in the case of edges of a part, limited to ensure a sharp corner and as such improving part quality.
The clever aspect of the Multi Jet Fusion printing process is the combination of fusing and detailing agent”
The second and equally important part of the Multi Jet Fusion printing process is the concept of a voxel. We are aware of what a pixel is; the difference between this and a voxel is the latter has a volume aspect to it. Think of the two-dimensional pixel 80 microns by 80 microns in size, add the third aspect of a height of 80 microns and you have a voxel.
It is these voxels that are built up layer by layer making the component. The potential of the voxel principle is however quite mind blowing. HP has a vast vison for this concept, consider the fact with the ability to control the content of each voxel, you could have different mechanical properties in different areas of the same component. Tensile strength, hardness and flexibility are just some of the properties that could be controlled.
Multi Jet Fusion technology uses a combination of fusing and detailing agent
You could change the surface texture of a part, its opacity, coefficient of friction, colour and even electrical and thermal conductivity through the one component in one manufacturing process: quite thought provoking.
The more mundane but nonetheless important elements of the Jet Fusion 4200 is the actual hardware which applies the materials that when activated produce the component. Basically, it comprises of a 3D printer, build unit and processing station.
Firstly, the build unit is loaded with the materials needed for the production of the desired part in an automated manner in the processing unit and then wheeled into the 3D printer unit. As described above, the materials are applied in the 3D printer in a nested configuration inside the build unit.
Once this 80 micron layering process has been completed up to a depth of 380mm, the build unit is removed from the 3D printer and taken back to the processing unit. The whole build unit is cooled at a controlled rate to ensure the parts are all reduced to room temperature without damaging or distorting them.
A number of 3D printers require additional space to break out the parts from the unfused build materials and there is the need to clean and finish the components off line. The clever aspect of the processing unit is the parts are broken out and cleaned in it, taking the advantage of recycling material that has not been used in the fusion process. This not only allows for a clean and operator friendly operation, but the amounts of waste can be kept to a minimum.
Costs for the materials used in the 3D printing process are not cheap so the holistic approach taken by HP towards the Jet Fusion 4200 with the 3D printer, build and processing unit make the manufacture of new complex components both possible and from a cost aspect, viable.
Obviously sat behind the printer are a number of software tools and interfaces to make the processing of parts seamless. The use of a number of build units makes the manufacturing process continuous as well ensuring the Jet Fusion 4200 is constantly working.
The process of Additive Manufacturing is now a well-established industry; with players such as HP producing equipment like the Jet Fusion 4200 and its other stable mates ensures the boundaries of the process are pushed to new horizons.
Brian Sims principal consultant, Metis Print Consultancy, www.metis-uk.eu
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