The Viennese start-up Printstones has been working on automation in construction operations since 2017. The focus is on the development of a 3D printing process for the automated production of concrete objects suitable for construction sites, which attracts attention with two unusual features: it is mobile and prints concrete and other cementitious materials that are used on the construction site. Conventional formwork elements are therefore a thing of the past.

Dr. Herwig Hengl is the founder of the TU Wien spin-off. He first came into contact with additive manufacturing around five years ago as a member of staff at the Institute of Mechanics of Materials and Structures: "We came up with this idea when we developed a simulation tool that can be used for stress and deformation analyses of stressed components. To verify the simulation results, the initially virtual components had to be recreated and loaded. As this is a very cost-intensive and time-consuming process, we were looking for a way to automatically produce the components directly from 3D models," recalls the young entrepreneur. Ideally, of course, this should take place directly at the final place of use: on the construction site of the future.

The Printstones founders were able to beat around 200 other start-ups with their business idea in a selection process organized by the university incubator INITS. The business model was then validated using qualitative and quantitative experiments and the development of "Printstones X1" was launched.

Important component in the 3D concrete printer: the tool changer from Gimatic © Printstones

Gimatic supplies the tool changing system for the 3D printer. Managing Director Johannes Lörcher even sees an application for himself in this use case: "3D printing is very much on the rise and you read more and more about new developments for the construction industry. I think the idea of printing building blocks is great - even if printing bricks is not yet possible due to regulations. But for our current new building in Hechingen, we could soon make very good use of such a printer for the many areas of paving stones. Johannes Lörcher assumes that such applications in the non-industrial sector will increase significantly with the further development of cobots.

One cubic meter of concrete with free geometry
The Printstones X1 is an early prototype of a mobile construction site 3D printer. It can currently be used to print concrete elements up to a size of around one cubic meter. The robot can be used both outside and inside. It eliminates the need for conventional shuttering by precisely placing and consolidating defined volumes of material in successive layers using a computer-controlled positioning process.

The 3D printing process consists of two general steps: 3D modeling and component printing. During path generation, various methods are implemented to generate robot trajectories. In general, each layer consists of an outer contour and a filling pattern, which can be designed as honeycomb structures or space-filling curves. Material preparation is fully automated via an upstream mini concrete plant. The recipe can be varied during the printing process, for example to print high-strength material in areas subject to heavy loads. With this technology, components from batch size 1 can be printed in variable shapes.

Tool changer with a key role
"Gimatic recognized the potential of Printstones early on and supported us with a suitable offer," says the founder. In addition to the 3D printing nozzle, the Printstones X1 currently has another tool for measuring the surface on which the print is made. The tool changer is therefore an important part of the system and is necessary for the fully automatic changeover between the tools.

"This application shows once again how practical it is to have a local contact," recalls Johannes Lörcher. "Our technical consultant Lars Janser from our branch in Graz visited the start-up in Vienna after initial contact from Printstone, advised the young entrepreneurs and convinced them. Our tool changer made it easy for him: the main arguments were certainly that it is very compact and offers super-simple control".

The Viennese company also sees a future application for Gimatic's grippers in its construction site robots. © Printstones

Profile of the tool changer
The all-electric EQC75 tool changer is suitable for changing applications with payloads of up to ten kilograms. It is mainly used in handling and linear robots for industrial applications that work mechatronically and do not use pneumatics at all. With its compact dimensions of 75 x 145 x 60 millimetres, it weighs just 1.1 kilograms. This means that it fits into the tight installation spaces of many small robots in the weight class up to five kilograms, for example. The EQC75 is controlled via the tried-and-tested 24-volt I/O circuit. Programming or additional control is not necessary. Its maximum torque is 150 Newton meters, the maximum tensile force is 2,000 Newtons and the maximum payload is ten kilograms.

For users who do not want to change over completely, it is easy to switch between electric and pneumatic, as the changeover system has four air connections. It has also been equipped with integrated sensors for position monitoring. The signal output is via the main cable. The signals from the sensors and the power supply can be transmitted using the 24-pin connector and the eight-pin cable. Thanks to an associated, compatible adapter, which is certified to ISO 9409-1, third-party products can also be connected. Retrofitting is also possible without any problems.

3D printing reduces_{CO2 emissions}
"After water, concrete is the material most used by humans, but at a high price. Cement production is responsible for around eight percent of global_{CO2 emissions}," Dr. Hengl points out. The proportion of_{CO2 emissions} from aviation is comparatively low at 2.6 percent. "Our goal should therefore be to reduce cement consumption wherever possible. Concrete 3D printing offers the possibility of eliminating low-stress zones of a component and thus saving material."

The system is designed as a multi-tool device. The concrete 3D pressure nozzle is therefore one of many possible tools. Further tools are to be developed in joint development projects with future users and customers.

"We are primarily involved in research and development and try to involve future customers as much as possible. We work exclusively with local partners such as architectural firms, industrial designers, building owners and contractors. We still have some pioneering work to do with the latter group, as the construction industry, which accounts for around seven percent of the global market, invests far less in research and development than the average of other industries," Herwig Hengl points out.

The all-electric tool changer from Gimatic is suitable for a wide range of applications. © Gimatic

"Our vision, or should I say mission, is the automation and optimization of construction processes. We want to reduce monotonous activities on the construction site with our technology and relieve construction workers. A good example is laying paving stones. Nobody enjoys spending eight hours a day on their knees in a stooped position laying bricks. With the mobile 3D printer, these stones can be printed directly onto the upper base layer of the road structure - laying is then no longer necessary," says Herwig Hengl, pointing out one of the possibilities.

Printstones is currently working as a contractor on pilot projects in the construction sector; within five years, the start-up aims to have completed the transition to a system provider. The future goal is to provide hardware, software and, in particular, building materials.

The Viennese company also sees a future application for the Gimatic grippers in their construction site robots. For example, they can imagine using them to insert reinforcement elements or other installation components. At Gimatic, the application is part of a series of other exciting applications. In addition to picking strawberries or collecting snails in the agricultural industry, concrete parts will also be gripped safely, reliably and efficiently in the future. as

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