Binder Jetting: A Comprehensive Guide to the Additive Manufacturing Process
07 Jul, 2023
ExOne binder jetting print head (credit: ExOne)
Binder jetting is accurate, fast, and more affordable than powder bed fusion processes like DMLS. Here we examine the process, its advantages and disadvantages, and its most promising applications.
Binder jetting is an innovative additive manufacturing process that has gained significant traction in recent years due to its ability to create complex parts with a high degree of design freedom. Popularized by binder jetting specialists like ExOne and Voxeljet, 3D printing giants like 3D Systems and GE Additive, and disruptors like Markforged and Desktop Metal, this 3D printing technology utilizes a liquid binder to selectively join powder particles layer by layer, forming a solid object.
First developed in the early 1990s, mostly by researchers at MIT, binder jetting has emerged as a versatile manufacturing method, compatible with a range of materials, including metals, ceramics, and sand.[1] As industries continue to adopt this technology, binder jetting is poised to play a crucial role in the future of manufacturing, enabling rapid prototyping, production of intricate components, and customization of products to meet specific customer needs.
This article serves as a comprehensive guide to the binder jetting 3D printing process. It looks at the main characteristics of the process, its benefits and limitations, its key current applications, and possible future applications.
The Binder Jetting Process
Overview of the Process
Binder jetting — sometimes called “binder jet 3D printing” or “powder bed and inkjet” — is a layer-by-layer additive manufacturing process that involves the selective deposition of a liquid binder onto a bed of powder material.
The process begins with the spreading of a thin layer of powder material, typically ranging from 20 to 100 microns in thickness, onto the build platform. A print head, similar to those used in inkjet printers, then moves across the powder bed, depositing the binder according to the digital design file. The binder acts as an adhesive, binding the powder particles together to form a solid layer of the object.
Once a layer is completed, the build platform is lowered, and a new layer of powder is spread on top of the previous one. The unbound powder surrounding the object acts as a support material, eliminating the need for additional support structures. The print head then deposits the binder onto the new layer, continuing the process until the entire object is built.
After the printing process is complete, excess powder is removed, and the part may undergo additional post-processing steps, such as infiltration, sintering, or surface finishing, to achieve the desired mechanical properties and surface quality.
Materials Used in Binder Jetting
Binder jetting is compatible with a fairly narrow but interesting range of materials, which contributes to its versatility in various applications. The choice of material depends on the desired properties and intended use of the final product. Some of the most common materials used in binder jetting include:
Metals
Binder jetting can process a variety of metal powders, such as stainless steel, tool steel, Inconel, titanium, and aluminum. Parts produced using metal binder jetting typically exhibit high strength, durability, and resistance to wear and corrosion once they have been post-processed. Researchers have noted that grades of stainless steel 3D printed using binder jetting equipment can possess equivalent or superior mechanical properties compared to cold worked stainless steel.[2] Such properties make metal binder jetting suitable for applications in aerospace, automotive, and medical industries. For instance, binder jetting can be used to create lightweight, high-strength components for aircraft engines or customized implants for medical procedures. Innovative 3D printer companies Desktop Metal and Markforged both offer metal binder jetting systems, as does GE Additive with the Series 3.
Ceramics
Ceramic materials, such as alumina, zirconia, and silicon carbide, can also be processed using binder jetting. Ceramic parts produced through this method exhibit excellent hardness, wear resistance, and thermal stability. These properties make them ideal for applications that require high-temperature resistance or electrical insulation, such as in the electronics, energy, and automotive sectors. For example, binder jetting can be employed to manufacture heat-resistant components for gas turbines or insulating parts for electrical devices. ExOne and Voxeljet are popular providers of ceramic binder jetting printers.
Sand
Binder jetting is particularly well-suited for processing sand materials, such as silica sand and synthetic sand. Sand parts produced using binder jetting are commonly used for creating molds and cores in the foundry industry, i.e. for sand casting. The process allows for the rapid production of complex sand molds, which can be used to cast metal parts with intricate geometries. This capability significantly reduces the lead time and cost associated with traditional mold-making techniques, such as pattern making and core assembly. ExOne and Voxeljet each offer sand binder jetting printers.
Binder Jetting 3D Printers
Binder jetting machines consist of several key components that work together to facilitate the printing process. These components include the build platform, powder bed, print head, powder feeding system, and binder supply system.
Build platform: The build platform is the surface on which the first layer of the object is printed. It moves vertically during the printing process, lowering incrementally after each layer is completed to accommodate the addition of new powder layers.
Powder bed: The powder bed is the area above the build platform and below the print head where the object is formed and surrounded by powder. It is crucial to maintain a consistent and even layer of powder throughout the process to ensure accurate and high-quality prints. The structure that encloses the powder is sometimes called the build box.
Print head: The print head is responsible for depositing the binder onto the powder bed. It typically consists of an array of nozzles that can selectively dispense the binder according to the digital design file. The print head moves horizontally across the powder bed, depositing the binder in a precise and controlled manner. Print heads vary by machine, but some can deposit material in many places at once — unlike a laser or extrusion nozzle — making the process very fast.
Powder feeding system: The powder feeding system supplies the powder material to the powder bed. It typically consists of a powder reservoir, a piston for pushing powder upwards, and a roller or recoater, which spreads the powder evenly across the build platform. The recoater ensures a consistent layer thickness, which is essential for accurate and high-quality prints.
Binder supply system: The binder supply system stores and delivers the liquid binder to the print head. It typically includes a binder reservoir, pump, and tubing that connects the reservoir to the print head. The binder supply system must maintain a consistent flow of binder to the print head to ensure accurate deposition and prevent clogging of the nozzles.
Together, these components enable the binder jetting process to create complex and intricate parts with a high degree of precision and accuracy. Proper maintenance and calibration of the equipment are essential to ensure optimal performance and consistent results.
Some of the most popular binder jetting 3D printers on the market include:
ExOne S-Max Pro
Voxeljet VX1300 X
Desktop Metal Production System P-1
Markforged PX100
3D Systems ProJet CJP 660Pro
GE Additive Series 3
Advantages of Binder Jetting
Rapid Material Deposition
During the binder jetting process, the print head can rapidly deposit binder in multiple places, as it has several nozzles rather than a single point of deposition (such as a laser or an extrusion nozzle). Some binder jetting 3D printers — certain machines from Desktop Metal, for example — can deposit binder across the entire powder bed in a single pass.
No Supports
In binder jetting, the unbound powder surrounding the printed part acts as a support material, eliminating the need for additional support structures. This feature not only reduces material usage and waste but also simplifies the design process and shortens the overall build time. In contrast, other additive manufacturing processes, such as SLM or stereolithography (SLA), often require the design and printing of support structures, which can increase both the production time and post-processing efforts.
Low Temperature
Unlike some other additive manufacturing processes, such as selective laser melting (SLM) or electron beam melting (EBM), binder jetting does not rely on melting and solidification of the material. Instead, it uses a liquid binder to join the powder particles. This reduces the cost of the process, as it does not require a high-power laser, and also enables the printing of materials that do not respond to laser melting or sintering.
Large Build Area
Binder jetting machines typically have large build volumes, enabling the printing of large components or simultaneous production of multiple parts within a single build. This capability allows for efficient batch production, reducing the overall production time per part. Furthermore, since the binder jetting process does not involve high-energy lasers or electron beams, there is minimal risk of thermal distortion or warping, even when printing multiple parts in close proximity. This feature enables manufacturers to optimize the build volume and achieve higher production efficiency.
Material Selection
Another notable advantage of binder jetting is its unique material selection. The process can accommodate unusual 3D printing materials such as ceramics and sand, making it suitable for various applications across different industries.
Limitations and Challenges of Binder Jetting
Post-Processing Requirements
Despite its numerous advantages, binder jetting also has some limitations and challenges, one of which is the need for post-processing steps to achieve the desired mechanical properties and surface finish of the final product. These post-processing requirements can add time and cost to the overall production process.
Typical post-processing steps for binder jetting include:
Infiltration: Parts produced using binder jetting have an inherently porous structure. To improve the mechanical properties and reduce porosity, an infiltration process is typically employed. In this process, a secondary material, such as a low-melting-point metal or polymer, is infiltrated into the porous part, filling the voids and increasing the part's density. While infiltration can enhance the mechanical properties, it also adds complexity and additional steps to the production process.
Sintering: In some cases, binder jetting parts may undergo a sintering process to improve their mechanical properties and dimensional accuracy. Sintering involves heating the part to a temperature below its melting point, causing the powder particles to fuse together and form a denser, more cohesive structure. However, sintering can also introduce thermal stresses and potential distortion. According to Mostafaei et al., “A major factor that contributes to distortion during sintering is differential shrinkage rates within the part due to thermal gradients. Any unpredictable shrinkage rate and distortion will result in the final part with inaccurate geometry and undesirable properties.”[3]
Surface finishing: Parts produced using binder jetting typically exhibit a rough surface finish. To achieve a smoother surface finish, additional post-processing steps, such as bead blasting, tumbling, or polishing, may be necessary. These steps can increase the overall production time and cost, particularly for parts with complex geometries or hard-to-reach surfaces.
Surface Finish and Resolution
Another limitation of binder jetting is the surface finish and resolution of the printed parts. The surface finish of binder jetted parts is typically rougher than those produced by other additive manufacturing methods, such as selective laser melting (SLM) or stereolithography (SLA), due to the internal and external porosity of the parts.
The surface roughness of binder jetted parts is influenced by factors such as powder particle size, layer thickness, and binder droplet size. Smaller powder particles and thinner layers can result in a smoother surface finish, but they may also increase the build time and the likelihood of powder agglomeration or clogging of the print head nozzles. To achieve a smoother surface finish, additional post-processing steps, such as bead blasting, tumbling, or polishing, may be necessary, which can increase the overall production time and cost.
The resolution of binder jetted parts is determined by the accuracy of the print head and the size of the binder droplets. While modern binder jetting machines can achieve high resolutions — high-end systems from ExOne, for example, have a voxel size of 30 microns — they may still be limited in their ability to reproduce extremely fine details or sharp edges. This limitation can be particularly challenging for applications that require high-precision components, such as in the electronics or medical industries. In such cases, other additive manufacturing methods, such as SLM or SLA, may be more suitable for achieving the required level of detail and accuracy.
Recommended reading: The Comprehensive Guide to Surface Finish Techniques, Standards and Applications
Mechanical Properties
Another challenge associated with binder jetting is achieving the desired mechanical properties in the final product. Parts produced using binder jetting can exhibit lower strength, ductility, and fatigue resistance compared to those manufactured using traditional methods, such as casting or forging. This limitation is primarily due to the presence of porosity.
Binder jetting parts often have a porous structure due to the presence of unbound powder particles. This porosity can negatively impact the mechanical properties of the part, such as tensile strength, ductility, and fatigue resistance. While post-processing steps like infiltration and sintering can help reduce porosity and improve mechanical properties, achieving the same level of performance as parts produced using traditional methods or other 3D printing technologies like DMLS can be challenging.
The layer-by-layer deposition process used in binder jetting can also influence the mechanical properties of the final part. The process can result in anisotropic properties, meaning that the part's strength and ductility may vary depending on the orientation of the layers — although this is a problem inherent to most 3D printing technologies. This anisotropy can be particularly problematic for parts subjected to complex loading conditions or those requiring consistent performance in multiple directions.
Applications of Binder Jetting
Industry | Example Parts | Materials |
Foundry | Casting cores and molds | Sand |
Medical | Porous implants | Titanium |
Automotive | Engine components | Technical ceramics |
Rapid Prototyping
Binder jetting has found widespread use in rapid prototyping due to its ability to quickly produce complex parts with minimal design constraints. The layer-by-layer deposition process enables the creation of intricate geometries and internal structures that would be difficult or impossible to achieve using traditional manufacturing methods. This capability allows designers and engineers to rapidly iterate on their designs, test new concepts, and optimize part performance.
In the early stages of product development, binder jetting can be used to create functional prototypes that closely resemble the final product in terms of geometry, material properties, and surface finish. These prototypes can be used for design validation, fit and function testing, and assembly verification, helping to identify potential issues and make necessary design changes before moving on to full-scale production.
Binder jetting's ability to produce multiple parts simultaneously also contributes to its effectiveness in rapid prototyping. By printing several design iterations or variations within a single build, engineers can quickly evaluate different design options and make informed decisions about the best path forward.
Production of Complex Parts
Binder jetting is particularly well-suited for the production of complex parts with intricate geometries and internal features. The process offers several advantages over traditional manufacturing methods, such as casting, machining, or forging, when it comes to producing parts with challenging designs.
Binder jetting enables the creation of parts with complex internal geometries, such as lattice structures, honeycomb patterns, or conformal cooling channels. These features can enhance the performance of components by reducing weight, improving heat dissipation, or increasing strength-to-weight ratios. For example, aerospace components designed with lightweight lattice structures can help reduce fuel consumption and emissions, while conformal cooling channels in injection molding tools can improve cycle times and part quality.
The binder jetting process also allows for the production of parts that integrate multiple components into a single, monolithic structure. This capability can simplify assembly processes, reduce the number of individual components required, and improve the overall performance and reliability of the final product. For instance, binder jetting can be employed to manufacture complex engine components that integrate multiple parts, such as cooling channels, structural elements, and mounting features, into a single, cohesive design.
Customization and Personalization
Binder jetting technology enables a high degree of customization and personalization in the production of parts and products. This capability is particularly valuable for industries and applications that require unique, tailor-made solutions or individualized designs.
Binder jetting allows for the production of customized components that meet specific performance requirements or design constraints. For example, in the aerospace and automotive industries, binder jetting can be used to create lightweight, high-strength components with complex internal geometries, such as lattice structures or honeycomb patterns. These custom-designed components can help improve fuel efficiency, reduce emissions, and enhance overall performance.
In the medical field, binder jetting can be employed to manufacture patient-specific implants, prosthetics, and orthotics. By using patient-specific data, such as CT or MRI scans, binder jetting can produce implants and prosthetics that are tailored to an individual's unique anatomy, ensuring a better fit and improved comfort. This customization can lead to better patient outcomes and reduced recovery times.
Future Developments in Binder Jetting
Advancements in Materials and Binders
As binder jetting technology continues to evolve, significant advancements are expected in the development of new materials and binders. These advancements will further expand the range of applications for binder jetting and improve the performance of printed parts.
Researchers and manufacturers are actively exploring the use of new materials in binder jetting, including advanced metal alloys, ceramics, and composites. These materials can offer improved mechanical properties, such as increased strength, wear resistance, or thermal stability, making them suitable for more demanding applications in industries like aerospace, automotive, and energy. Additionally, the development of new materials can enable the production of parts with unique properties, such as tailored thermal expansion coefficients, electrical conductivity, or magnetic properties.
The development of new binder formulations is another area of ongoing research in binder jetting. Improved binders can offer better adhesion between powder particles, resulting in stronger parts with fewer defects. Furthermore, advancements in binder technology can enable the use of lower curing temperatures, reducing the risk of thermal stresses and distortion during post-processing. Researchers are also exploring the use of environmentally friendly, biodegradable binders, which can help reduce the environmental impact of binder jetting processes.
Another promising area of development in binder jetting is the ability to print parts using multiple materials within a single build. This capability can enable the production of parts with graded or functionally graded materials, where the composition of the material changes gradually throughout the part. Multi-material printing can be used to create parts with tailored mechanical, thermal, or electrical properties, opening up new possibilities for innovative designs and applications.
Improvements in Equipment and Process Control
Advancements in binder jetting equipment and process control have played a significant role in enhancing the capabilities of this additive manufacturing technology. These improvements have led to higher-quality parts, increased production efficiency, and expanded material options.
Modern binder jetting machines are equipped with advanced print head technology that enables precise control over the deposition of binder droplets. These print heads can achieve high resolutions, typically in the range of 50 to 100 microns, and can be adapted to work with a variety of binder formulations. The improved accuracy and versatility of print head technology have contributed to the production of parts with better surface finish, resolution, and mechanical properties.
Innovations in powder handling and recoating systems have led to more uniform and consistent powder layers, which in turn result in better part quality and dimensional accuracy. Advanced recoating systems can minimize the risk of powder agglomeration, clogging, or uneven spreading, ensuring that each layer is deposited with the desired thickness and uniformity.
The integration of advanced sensors, cameras, and software tools in binder jetting equipment has enabled real-time monitoring and control of the printing process. These systems can detect and correct potential issues, such as powder bed irregularities, binder saturation levels, or temperature fluctuations, ensuring that the process remains stable and consistent throughout the build. This level of process control contributes to the production of parts with improved dimensional accuracy, surface finish, and mechanical properties.
New Applications and Industries
As binder jetting technology continues to evolve and improve, it is opening up new applications and opportunities across various industries. The combination of design freedom, material versatility, and the ability to produce complex parts quickly and cost-effectively makes binder jetting an attractive option for a wide range of applications.
Construction and architecture
Binder jetting has the potential to revolutionize the construction and architecture industries by enabling the production of large-scale, customized building components and structures. For example, binder jetting can be used to create intricate facade elements, lightweight structural components, or even entire buildings using materials such as concrete or geopolymers. This technology can help reduce construction time, material waste, and labor costs while enabling architects and designers to explore new design possibilities.
Electronics
In the electronics industry, binder jetting can be employed to produce complex, high-precision components, such as heat sinks, connectors, or circuit board substrates. The ability to create parts with intricate internal geometries and customized thermal properties can help improve the performance and reliability of electronic devices, while also reducing manufacturing costs and lead times.
Energy and environment
Binder jetting can play a significant role in the development of sustainable energy solutions and environmental technologies. For example, the technology can be used to produce advanced catalysts and filters with complex internal structures, which can enhance the efficiency of chemical reactions or improve the performance of air and water purification systems. Additionally, binder jetting's compatibility with a wide range of materials, including metals, ceramics, and composites, enables the production of components for renewable energy systems, such as wind turbines, solar panels, or fuel cells.
Food and agriculture
Binder jetting is also finding applications in the food and agriculture industries, where it can be used to create customized food products, packaging, or agricultural tools. For example, binder jetting can be employed to produce food products with tailored nutritional content, texture, or flavor profiles, offering new possibilities for personalized nutrition and food innovation.
As binder jetting technology continues to advance, it is likely that even more applications and industries will emerge, further expanding the potential of this versatile and powerful additive manufacturing method.
Recommended reading: Enhancing Industrial Processes through Design for Manufacturing: A Comprehensive Guide
Conclusion
Binder jetting is a versatile and rapidly evolving additive manufacturing technology that offers numerous advantages, such as design freedom, speed, and material versatility. While there are challenges associated with surface finish, resolution, and mechanical properties, ongoing research and development efforts are addressing these limitations and expanding the range of applications for binder jetting. Advancements in materials, binders, and multi-material printing will continue to drive the growth and adoption of this technology across various industries, including aerospace, automotive, medical, and consumer products. As binder jetting technology matures, it is expected to play an increasingly important role in the future of manufacturing, enabling the production of innovative, customized, and complex parts that were previously unattainable using traditional methods.
Frequently Asked Questions
Q: What is binder jetting?
A: Binder jetting is an additive manufacturing process that uses a liquid binding agent to selectively bind powder particles together, layer by layer, to create a three-dimensional part. The process is compatible with a wide range of materials, including metals, ceramics, and sand.
Q: What are the advantages of binder jetting?
A: Binder jetting offers several advantages, such as design freedom, speed and efficiency, and compatibility with unusual 3D printing materials like sand and ceramics. The process enables the production of complex parts with intricate geometries and internal structures, while also allowing for rapid prototyping and the use of various materials.
Q: What are the limitations and challenges of binder jetting?
A: Some limitations and challenges of binder jetting include post-processing requirements, surface finish and resolution, and mechanical properties. Parts produced using binder jetting often require additional post-processing steps, such as infiltration or sintering, to achieve the desired mechanical properties and surface finish.
Q: What are some applications of binder jetting?
A: Binder jetting is used in a variety of applications, including rapid prototyping, production of complex parts, and customization and personalization of products. The technology is particularly well-suited for industries that require unique, tailor-made solutions or individualized designs, such as aerospace, automotive, medical, and consumer products. Metal and ceramic binder jetting is suited to smaller, high-quality components, while sand binder jetting is ideal for large foundry tools like molds and cores.
Q: What are some future developments in binder jetting?
A: Future developments in binder jetting include advancements in materials and binders, as well as multi-material printing. These advancements will further expand the range of applications for binder jetting and improve the performance of printed parts.
References
[1] Gibson I, Rosen D, Stucker B, Khorasani M, Gibson I, Rosen D, Stucker B, Khorasani M. Binder jetting. Additive manufacturing technologies. 2021:237-52.
[2] Li M, Du W, Elwany A, Pei Z, Ma C. Metal binder jetting additive manufacturing: a literature review. Journal of Manufacturing Science and Engineering. 2020 Sep 1;142(9):090801.
[3] Mostafaei A, Elliott AM, Barnes JE, Li F, Tan W, Cramer CL, Nandwana P, Chmielus M. Binder jet 3D printing—Process parameters, materials, properties, modeling, and challenges. Progress in Materials Science. 2021 Jun 1;119:100707.