3D Printing in the Fast Lane
Additive and Subtractive Manufacturing of Large-Volume Plastic Components
SEAM (Screw Extrusion Additive Manufacturing) opens up new perspectives for additive manufacturing. The process was developed by Metrom GmbH in Hartmannsdorf, together with the Fraunhofer Institute for machine tools and forming technology (IWU) in Chemnitz, both Germany.
Employing this process, plastic pellets are molten in a modified extrusion screw. Via a die, the material is then applied to a construction platform that can be swiveled over five axes. The plastification unit is fixed to the main mandrel of a machine tool, while the construction platform is driven by a Pentapod 5-axis parallel kinematic unit by Metrom. The unit offers outstanding dynamics, low moving mass and, along with this, high accuracy of positioning and path. This enables process speeds up to 900 mm/s and acceleration up to 10 m/s².
Output Rate up to 100 Times Higher
There are often some major downsides to additive production of prototypes and small series, i.e. low printing speeds, while the used filaments are expensive and necessary secondary finishing is time-consuming. As opposed to this, according to Metrom head of sales Marcus Witt, process speeds of the SEAM technique are up to ten times higher and output rates per hour are up to 100 times higher, as compared to the FDM/FLM processes currently used.
Offering high degrees of freedom, the 5-axis parallel kinematic machine tool enables the production of complex geometries such as protuberances of up to 65° at high accuracies and without any additional supportive structures. The new system can even apply prints to the surfaces of existing moldings. According to Witt, there are more fields of application thanks to the fact that components can be produced in accordance with the load path.
Per hour, the unit presses up to 7 kg of plastic material through the hot die with its 1 mm diameter. Rather than processing a restricted number of filaments, the process can handle a variety of thermoplastic, and even fiber reinforced, materials. If using standard pellets here, costs are significantly reduced. Even recycled materials obtained from waste can easily be processed, says Witt.
And the system includes another benefit: The high-speed process makes it possible to connect additive and subtractive techniques for the production of plastic components. Linking the 3D printing process to a subsequent step of surface treatment (e.g. milling) in a fixture opens up numerous options, even for very complex components.
Fraunhofer-Institut für Werkzeugtechnik und Umformtechnik IWU
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