High Speed Sintering (HSS) for the flexible production of functional components
voxeljet has officially launched its new High Speed Sintering (HSS) technology. HSS is a physical binder-jetting process that allows the tool-less production of functional prototypes as well as final consumer parts. Examples of use include product packaging or interior fittings for automobiles. At this year's formnext trade fair 2017 in Frankfurt, visitors were able to view the technology for the first time live at the voxeljet AG booth.
The HSS process combines the advantages of two existing additive processes: selective laser sintering and binder jetting. While laser sintering, already allows many powder materials to be sintered into functional prototypes today, binder jetting impresses with its high printing rates in terms of size and speed of the construction site. High Speed Sintering thus allows the economical processing of larger plots and a wider selection of materials.
The High Speed Sintering Process
In the HSS process, a thin layer of plastic granulate, such as PA12 or TPU, is applied on to a heated building platform. An inkjet print head then moves over the entire surface of the platform and moistens the areas of the construction site with infrared light-absorbing ink, on which the prototype is to be produced. The building platform is then irradiated with infrared light. The wetted areas absorb the heat, which sinters the powder layer underneath. However, the unprinted powder remains loose. After sintering, the building platform is lowered by one layer thickness. This process is repeated until the assembly of a component is completed. The sintered parts are then cooled down in a controlled manner in the installation space before they can be removed and unpacked. In contrast to laser-based processes, the entire building platform can be printed in just one go, which enables a constant layertime time, irrespective of the size and complexity of the parts. Inert gas atmosphere is also not necessary for the HSS printing process. The large-area print head has a resolution of 360 dpi achieved through 3000 individually controllable nozzles, which allows the smallest details to be manufactured with high precision of the edges. In combination with a minimum layer thickness, the resolution of the print head enables the production of the finest structures with wall thicknesses of up to 0.15 mm. Since the HSS printing process requires no other fluids than ink, material costs can also be reduced to a minimum. The high quality of the components is also underlined by high accuracy and impressive definition of the edges.
The VX200 HSS from voxeljet offers unprecedented open sourcing possibilities. With the new ProPrint control software, users can program and insert customer-specific macros in just a few steps to adapt the printer to the desired material parameters and process operations. In addition, the software can also be used for individual process data mining, enabling the recording and evaluation of a wide variety of process data as required. Moreover, the user can process different powder materials, as the powder material does not necessarily have to be purchased from voxeljet. With regard to layer thickness, it is currently possible to vary between 80 - 100 µm, depending on the choice of material.
One of the first users of HSS technology is the chemical company Evonik Resource Efficiency GmbH. Sylvia Monsheimer, Head of Market Segment New 3D Technologies at Evonik, has been working with HSS technology for some time: "We want to process a wide variety of materials with our VX200: from PA12 and PA613 to PEBA. However, we are generally not limited in the materials portfolio. The HSS technology from voxeljet allows the interaction between material and machine to be optimized and thus the offering of the best possible material," says Monsheimer. “The providing of an open machine with such a high degree of flexibility in terms of material possibillities and a rapidly adaptable process such as Binder Jetting is, definitely a unique selling point.
With regard to materials different powders can be printed, given, that sufficient flow ability is ensured. This depends on the average grain size (30 - 70 µm average grain size), fine powder content and powder composition. Powders with low thermal conductivity can currently be processed up to a melting temperature of 190 °C, provided that they have a sufficient sintering window. Due to the fact that the heat input in HSS is gentle, a much larger selection of workable materials opens up than with previous processes.
The temperature management is carried out via the external Heat Control Unit (HCU), which monitors the temperature inside the pressure chamber at all times and automatically corrects it if necessary. The HCU is operated conveniently via touch display. All five individual heat sources within the printer can be individually controlled and adapted to the individual material properties.
Efficiency and scalability
“The VX200 is our entry-level model and therefore particularly well suited for this new technology. It offers the opportunity to exploit the full range of limitations and applications on a resilient and industrial machine. In addition to PA12, elastomers such as TPU can be printed. The open sourcing program allows everyone to use their machines for their own individual benefit. The variety of possible applications is more than impressive," says Dr. Ingo Ederer, CEO of voxeljet. “We see enormous potential for this technology. That's why we're already working on scaling the technology to our larger printers to ensure an even higher plateau of productivity."
Evonik also sees great potential for the future in this technology: "I am convinced that this technology is only at the beginning. The wide range of materials is trend-setting for this technology," says Monsheimer.
The VX200 is ideal for material developers, research institutes and OEM's to explore and exploit the diversity of materials in the field of thermoplastics and elastomers. In addition, it is easy to produce consumer parts that for direct use.