Credit: www.3dprintingmedia.network
After years of R&D, German industrial binder jetting 3D printer manufacturer voxeljet has perfected 3D printing for complex formworks and now sees the construction industry as a key growth area for its binder jetting technology in the future. The large format binder jetting process from voxeljet has been proven to be particularly helpful for complex 3D printed formworks, breaking away from traditional systems and their stringent geometrical limitation
In traditional construction, walls need to be positioned at a 90° angle (perpendicularly) to each other. Any protrusion, bend or offset requires special formwork, which is extremely labor-intensive and time-consuming. Three-dimensional curved construction elements are even more challenging. For these, the formwork must first be milled from wood or plastic, manually assembled and subsequently ground and coated several times. Since such formworks are usually made up of individual segments, the formwork contractor glues them together. In order to achieve a uniform concrete surface, it is then necessary to grind and seal the joints.
Using binder jetting 3D printing it becomes much simpler, faster and more accurate to produce even the most complex formworks. The primary advantage is that 3D printing enables the most complex formwork elements to be designed using CAD specifications. After the printing and infiltration process, the 3D printed formwork elements can be used just like conventional formwork.
Key Advantages
The advantages of 3D printed formwork for individual construction needs are numerous. The digital, effortless process significantly speeds up the building effort, especially in the case of multiple-curved concrete elements. Using 3D printing these can be manufactured more precisely and thus no time-consuming corrections – which may delay the entire construction process – have to be made.
Depending on the geometry, the formwork produced with powder binder jetting technology can be used up to 40 times. This reduces the costs per concrete surface for each additional use. voxeljet formwork elements withstand concrete casting pressure of up to 100 kN/mÇ and there are no limitations regarding used release agents and concrete.
If a three-dimensional shape is repeated – but in a different size, the 3D data can be easily digitally rescaled and used to create another mold. In this sense, voxeljet elements can provide valuable services as a master mold in the fabrication of polyurethane or silicone formwork matrices, such as those used for facades – regardless of the elements texture. Unlike for other 3D printing applications, size here is not a concern: the voxeljet VX4000 printing system (the largest industrial 3D printing system for sand molds in the world) can achieve build volumes of up to 8 cubic meters (4000 x 2000 x 1000 mm).
Topping Contour Crafting
Voxeljet’s Binder Jetting technology should not be mixed with contour crafting. This approach, invented by professor Koshnevis and commercialized by the Chinese company Winsun (not without some patent-related controversies), is used to erect an entire house or building element by extruding fast-hardening concrete with a robot.
However, the process has shown some significant limitations, especially when it comes to integrating reinforcements, creating three-dimensionally multi-curved concrete walls and producing components with undercuts or fine textures. Currently, this is only possible up to a certain angle of inclination. In addition, contour crafting is a low resolutions process which means that delicate structures and details cannot be reproduced
While the ultimate goal of contour crafting is to replace traditional construction processes entirely, voxeljet’s technology can be used to expand and optimize current proven construction methods, primarily by simplifying the manufacturing process for three-dimensional building elements today.
Doka: case and point
During the construction of the headquarters of the Sächsische Aufbaubank in Leipzig, (Germany), a semi-circular staircase with an intermediate platform was to be erected, which is mounted on a supporting wall. An incredibly complex and precise concrete formwork was required to give the staircase a smooth, uniform curve, The project managers entrusted the world-renowned formwork supplier Doka with this task.
After extensive evaluation and definition of the formwork design for the staircase, Doka categorized the different surfaces according to their complexity. Single-axis curved surfaces with cylindrical or conical shapes were formed conventionally. The specific feature of this staircase, however, was the triaxially curved surface, which represents the rounded overhang of the staircase to the inside of the supporting wall.
The production of such shapes with conventional craftsmanship is extremely time-consuming. Wooden bars have to be cut, bent into shape, fixed and bonded together. Subsequently, the surface must be sanded and smoothed several times before it is varnished twice. The result is a part whose load-bearing components have been assembled under tension and were manufactured out of organic materials. Under the influence of temperature and humidity fluctuations at the construction site as well as general weather conditions, wooden cracks can easily occur which visibly affects the quality.
This is where binder jetting 3D printing from voxeljet offers considerable advantages. Components can be produced quicker and with less engineering effort directly from 3D data. The 3D printed components are manufactured precisely and tension-free and are therefore dimensionally very stable. The homogeneous material offers additional quality assurance with regard to the weather conditions.
Voxeljet’s German service center 3D printed seven formwork panels from sand, with a wall thickness of just 21 mm. These were then infiltrated with epoxy resin in order to achieve the necessary rigidity. After sanding and coating by Doka, the formwork was ready for use.
One important aspect was that the three dimensional, curved voxeljet elements were designed in such a way that they could be perfectly combined with the standard Doka formwork on site. For example, the Doka staff had placed functional integrations such as drill holes and plug-in connectors in the data set. This enabled quick and efficient assembly of the formwork. The entire formwork was preassembled quickly and efficiently at the Doka plant.
An additional benefit of the post-treated epoxy-sand mixture is its weather and scratch resistance. The use of voxeljet formwork proved to be ideal in several ways: First, only a tenth of the usual assembly time was required. Second, the 3D printed components matched one hundred percent with Doka‘s CNC-cut Xlife panels when assembling the formwork elements. This hybrid approach ensured the cost-effectiveness of the formwork solution with 3D printed components. Third, the high precision of the fabrication was impressive, due to the consistent digital data processing of the 3D printed geometries from design to assembly.
After successful concreting and demolding, the casting results of the staircase could be compared. The result was astounding: the part of the staircase that was illustrated with voxeljet formwork showed very good casting results corresponding to the quality of the 3D printed elements. Neither bleedings nor concrete nests could be found. With hindsight, the Doka team say that it definitely might have made sense to use it on more surface areas. Doka is also convinced, that the voxeljet formwork can be used for construction sites with exposed concrete surfaces.
On-site binder jetting
voxeljet now offers manufacturing support for formwork elements worldwide. The company’s service centers in Germany, England, the United States, China and India can produce 3D formworks quickly and cost-efficiently.
Even shapes with complex geometries can be produced with virtually no restrictions. And since formwork is manufactured individually, it is possible to produce each one in such a way that it can be combined with almost any standard formwork system as a hybrid.
Users are also supported in detailed questions regarding the required data and the handling of the formwork. 3D printing allows the efficient and safe realization of multi-dimensional curved structures on the construction site and in the precast factory.
Why 3D printing is the future of construction
In its report on additive manufacturing in the construction industry, SmarTech Publishing made some very bold forecasts with the segments expected to generate upwards of $40 billion in yearly revenues by the 2030s. These forecasts are based on the huge size of the global construction industry (in the trillions of dollars) coupled with the very significant and clear advantages that 3D printing technologies can bring by streamlining and furhter automating the construction process.
The complete process is based on a closed data structure – from CAD planning to the finishing of the formwork element through 3D printing and CNC milling. Because components correspond to the digital model 1:1, their elements are custom-fit, which makes them easy to assemble. Higher accuracy also eliminates the need for manual rework on site.
Since the voxeljet formwork does not release resins (as is often the case with wood formworks) and does not otherwise change, the quality of the casting result is always consistent. The 3D printed formworks are extremely weather-resistant, with heat, moisture and cold having no influence on the reworked formwork elements. Unlike wood, they do not absorb water or yield (e.g. compared to plastic formwork).
Voxeljet enables the production of formwork elements with a total building volume of 4.00 x 2.00 x 1.00 m with a speed of 139 l/h. Building components can be nested digitally into the job box. This guarantees optimum utilization of the machines. Further scaling is possible without any problem.
Proven construction processes are not changed. Construction techniques and material characteristics which have proven over decades can be retained. The 3D printed formwork elements can also be combined with other formworks in hybrid approaches.
There are, of course, also challenges that need to be addressed in implementing binder jetting in formworks production. One is that the elements consist of a powder and a chemical binder and thus they must be disposed of separately. The disposal of the elements as hazardous waste could counteract the current trend for ecological construction.
In addition, depending on the geometry, voxeljet formwork is usually more cost-intensive than conventional formwork in a pure production environment. One of the greatest risks is, that the concrete industry, still dominated by conventional thinking, will consider this solution to be too radical
Building new possibilities
In addition to the manufacturing of complex concrete formworks, voxeljet’s binder jetting technology can also simplify additional areas of architecture. One is architectural modeling. Architects are creating ever more realistic models to present their projects to interested parties in a comprehensible way. This is a difficult, time-consuming and cost-intensive task. Digital plans with CAD systems have long been a standard feature of architectural practice. All relevant data specifications are already available in 3D in a data cloud and can easily be imported for 3D printing. It is therefore much faster and more affordable to create the models directly in 3D printing. Above all, voxeljet printing systems are able to reproduce the buildings in more detail than it would be possible with manual model making.
