During the construction of the headquarters of Sächsische Aufbaubank in Leipzig, Germany, a semi-circular staircase with an intermediate platform was to be erected on top of a supporting wall. In order to lend a smooth, uniform curve to the staircase, an incredibly complex but ultra-precise concrete formwork was required.
The project managers entrusted the formwork supplier Doka with this task. The Voxeljet 3D printing technique was applied to produce seven additional formwork panels from sand for which conventional methods were unsuitable owing to the panels’ complexity.
Ultra-precise components from the 3D printer
After extensive evaluation and definition of the formwork design for the staircase, the different surfaces were categorized according to their complexity. Uniaxially curved surfaces in cylindrical or conical shapes were formed conventionally. The specific feature of this staircase, however, is its triaxially curved surface, which represents the rounded overhang of the staircase to the inside of the supporting wall. Producing such shapes with conventional, craftsmanlike techniques is extremely tedious and time-consuming.
This is where 3D printing from Voxeljet offers major benefits. Components can be produced more quickly and with less engineering effort directly from 3D data. The 3D-printed components are manufactured with utmost precision and free from tension, which is why they provide a high degree of dimensional stability. The homogeneous material offers additional quality assurance in respect of the weather influence mentioned above.
Triaxially curved elements
Voxeljet applied the powder-binder jetting technique to 3D-print seven formwork panels from sand, each with a wall thickness of just 21 mm. The manufacturer then infiltrated the elements with epoxy resin in order to achieve the required rigidity. After sanding and coating by Doka, the Voxeljet formwork was ready for use. One important aspect was that the triaxially curved Voxeljet elements were designed in such a way that they could be easily combined with standard Doka formwork on-site.
For example, the Doka staff had placed integrated functional features such as drill holes and plug-in connectors in the relevant data records, which made it possible to preassemble the formwork quickly and efficiently at the Doka plant. Installation of the formwork on the construction site was very fast and efficient thanks to the high precision of the 3D-printed formwork.