3D Sand Printing—Sandbased Additive Manufacturing

Binder jetting is a cutting-edge additive manufacturing technique. In this process, fine particles—often foundry sand, though metal powders and ceramic particles are also used—are bound together with a special liquid binder. This binder, typically a resin or another specialized liquid ensures, that the particles stick together securely.

The process begins with a thin layer of sand being spread across a build platform. A print head then moves across the surface, spraying binder onto specific areas based on the component’s design, as determined by the CAD data. This targeted application ensures the binder is only applied where it's needed, shaping the component layer by layer with precision.

Once the binder is applied, a drying or curing phase solidifies the bond, ensuring the component has the strength it needs to maintain structural integrity. This step guarantees the finished product is durable and ready for use. The layering continues until the component is fully formed, after which post-processing steps are required to remove excess material and refine the piece, whether by strengthening it further or performing additional machining.

Advantages of Binder Jetting

Binder jetting stands out for its remarkable flexibility and cost-effectiveness, allowing for the efficient production of complex geometries without the need for traditional tools.
With binder jetting, there is precise control over the structure and density of the printed components through a careful dosage of binder and material. This precision enables the creation of even the most intricate details and complex cavities. For casting, this brings significant advantages: molds and cores can be directly produced from CAD data, eliminating the need for conventional tools or models. This not only saves time but also cuts costs in prototype development and small-batch production. The technology offers new creative freedom in component design, enabling shapes that would be impossible with traditional methods. As a result, binder jetting is becoming increasingly popular in toolmaking and for producing customized components.

More info

Video: Binder jetting in process

Binder jetting-projects:  

• Bavaria 2.0
• ConMon3D
  

Additive manufacturing with multiple stages for serial production

Fraunhofer IGCV explores the entire process chain of additive manufacturing for producing components used in casting application

Advantages of sand based additive manufacturing for cast parts along the entire process chain

Starting with material development, which generates new moulding materials and binder systems, processes are adapted, optimized or newly conceived. These are implemented in prototype test systems or implemented on an industrial scale at the customer's premises. With Sand Printing at the center, the entire process chain is always considered in order to bring the advantages of Additive Manufacturing to series production.

Material development for 3D printing

In contrast to Laser Beam Melting processes, a multi-stage additive manufacturing chain focuses on other material properties. For example, when the 3D printed part is used as a casting mold, the focus is on temperature resistance and process chain suitability. Short life cycles require special attention to be paid to the recyclability of the materials. The binder systems must not only meet the requirements of the casting process, but also be able to be processed by an Inkjet Print Head. Sand is also being closely examined, as this material must also be adapted to the specific requirements of both the casting world and processability in 3D printing. The working group at the Fraunhofer IGCV has methods from both worlds at its disposal: A fully equipped Moulding Materials Laboratory is supplemented by methods for characterizing particle materials, binder chemistry and the rheology of the binders developed.

Processes and process control

Parallel to material development, the Process Control is investigated in order to bring the material into the desired geometry. For this purpose, 3D Printing test stands are used, modified and parameterized for processing on a laboratory scale. Test specimens are produced in test stands or in industrial plants, which enable comprehensive documentation and evaluation of the basic material properties, as well as a well-founded discussion with experts from the casting industry. Customer processes are also analyzed and recommendations are made for increased process reliability and more dimensionally accurate moulds.

Special processes, such as slurry-based 3D Printing, represent a significant extension of conventional printing processes in terms of material properties and possible resolution. In addition to moulds for investment casting applications, this process variant can also be used to print components directly for the application, for example with aluminum.

Machine technology

The engineering of machine elements and entire printing systems enables the low-barrier implementation of process chains. To this end, the Fraunhofer IGCV uses the mechanical engineering expertise of its employees to implement new ideas for the design of components or process control, as well as to enable customers to map or improve their processes. The printing system, with its central element - the Inkjet Print Head, is a focus of research. Various commercially available inkjet printing modules are used and their wear is characterized. In the area of Powder Coating, systems are set up and their influence on print quality, for example the shifting of already printed areas, is clarified. These findings can be used to specifically increase performance parameters such as coating speed. Camera systems are used for Process Monitoring, which use Image Processing and AI methods to provide specific information on process stability.

Customer project for the development of a customized test setup for 3D Sand Printing:

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The Bavaria statue has stood watch over the Theresienwiese in Munich since 1850. To this day, the 18-meter-high, 87-tonne patroness of Bavaria is regarded as a technical masterpiece

150 years later, we at Fraunhofer IGCV have achieved another technical triumph with the creation of her doppelganger! Standing at approximately 1 meter tall and weighing 25 kg, Bavaria 2.0 is much smaller and lighter, but no less groundbreaking in foundry circles. This aluminum miniature was crafted using an innovative stack casting process, consisting of 53 individual parts. The casting molds were created through 3D sand printing—a method especially well-suited for complex structures.

The project not only replicated the Bavaria statue, but also showcased that the modular division of the mold allows for the production of highly intricate structures and components that would be difficult or even impossible to achieve with traditional casting molds. This makes the process incredibly versatile and forward-thinking for metal casting—whether for art, prototypes, or industrial applications. The Bavaria project demonstrates how 3D sand printing, or binder jetting, can be successfully applied in foundry practices.  

More info:

• Voxelguss Bavaria 2.0 (giessereitechnik-muenchen.de).
• Flyer (german lanuage): Bavaria im Voxelguss
• Press release (german language) 09/2024: »Becoming Bavaria«
  

In order to prevent expensive and time-consuming errors in additively manufactured components, the “ConMon3D” project is continuously monitoring the print head as a core component for Binder Jetting processes. Until now, the condition of key machine components in Binder Jetting has usually only been checked manually before the printing process. The aim is therefore to develop an easy-to-integrate module for Binder Jetting processes that saves effort and costs by enabling monitoring without significant hardware expenditure.

For example, images are taken with a process room camera inside a 3D Printer in order to obtain the required measurement data. This allows conclusions to be drawn about the expected component quality and processes to be readjusted accordingly.

Further information: to the “ConMon3D” project page