3D PRINTING PROCESS
The HP Multi Jet Fusion is currently the fastest and most economical 3D printing process for extremely high-quality prototypes, functional parts and small batches.
The HP MJF is predestined for the production of small batches (100 - 5,000 pieces). The delivery times are extremely short and the part quality in terms of balanced mechanical properties is unchallenged.
With its almost isotropic material properties, the technology offers a unique selling point in the field of additive plastics production. In addition, the parts are pressure-tight, making the technology perfect for functional parts.
Prototypes that closely resemble later injection molded parts are possible with the HP MJF process. You can thus check your component geometry with installation samples or decide directly for a 3D printed pre-production series.
The HP-PA12 has a very balanced profile of properties and is suitable for functional parts and prototypes due to its high stability and impact resistance.
This PA12 filled with 40% glass beads is used especially for components that require high rigidity and dimensional stability, such as housings.
The polyamide 11 from HP is tougher than PA12 and tears when force is applied instead of splintering. This is a crucial safety factor, especially in the automotive industry.
Parts that were produced using the HP MJF process come from the 3D printer in gray. Similar to the SLS process, untreated parts easily absorb dirt due to their rough surface properties and, if they come into contact with skin, also sebum, which makes the parts appear greasy after a certain period of use. Without a finish, we recommend untreated parts, mainly for prototypes and functional parts that are not exposed to strong skin contact.
Due to the gray basic color, HP MJF parts can only be colored in different colors to a limited extent. That is why we only color HP parts black. If a different color is required, we recommend using selective laser sintering. Harmless textile dye is used for dyeing, which penetrates the surface of the part during the dyeing process. The dyeing process is very simple. The necessary color pigments are dissolved in a heated water bath and then the gray HP MJF parts are added. After a certain time, the parts have absorbed the paint and can be removed again. This is followed by a short drying phase and the parts are ready for dispatch or further processing.
In vibratory grinding - also known as barrel finishing - the finished components are placed in a vibrating trough after powder removal, together with differently shaped whetstones. The vibrations generated in it cause stones and parts to move through. This produces uniform abrasion on the part, resulting in a homogeneous, smooth surface. However, this finishing process is not recommended for parts that require sharp edges, as these are broken and slightly rounded off in the process.
The surface of the finished printed parts is compressed again by the so-called compaction blasting. This gives the surface a slightly velvety and smooth structure, which, in contrast to untreated surfaces, is less scratch-sensitive and rough.
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How does the 3D printing technology work?At the beginning a thin layer of fine PA12 powder is applied to the construction platform. As can be seen in the video, the powder is applied from back to front and front to back. In the next step, the printing carriage moves over the prepared powder layer from right to left. The print carriage contains the HP thermal inkjet print heads and two energy sources. The leading energy source preheats the applied powder layer in order to ensure perfect temperature control for each layer. The temperature of the print layer is measured and controlled at over 900 measuring points throughout the work area. Immediately after the energy input, two different agents are applied via the print heads in order to print the respective part layers on the powder.
In the actual printing process, the fusing agent (black) is used to mark the areas that are later to be fused into a solid part. The second so-called detailing agent (transparent) is applied to the edges of the parts in order to weaken the melting process at the edges. This makes it possible to achieve very high accuracy, sharp edges and a smooth surface. After the application of the agents, the second energy source in the print carriage again applies heat to the print layer. Due to the physical fact that black areas absorb light (energy) more strongly than a white one, the powder is only fused in the areas printed with the black fusing agent. This process is now repeated layer by layer until the final part height is reached. The following figure shows the individual process steps:
HP has revolutionized 3D printing with the Multi Jet Fusion process. This was a very big step towards additive series production. It is not just the printing process that is revolutionary. All manual activities have also been standardized and optimized in such a way that continuous production is possible with a minimum of error. Powder preparation, recycling and filling of the printing units are handled by the HP Jet Fusion Processing Station.