Ceramics 3D Printing: Everything You Need to Know
As one of the oldest manufacturing materials, ceramics is a prominent aspect of the development of human civilisation. Since its first uses for pottery as a reliable material for food storage, along with pieces of art like statuettes for religious …
As one of the oldest manufacturing materials, ceramics is a prominent aspect of the development of human civilisation. Since its first uses for pottery as a reliable material for food storage, along with pieces of art like statuettes for religious purposes, ceramics never ceased to be relevant. On the contrary, with the rapid development of scientific practices and industrial processes in the latest decades, we’re still uncovering the unlimited potential these materials have to offer in performance.
And what do we mean by ceramics? What are those properties we consider valuable? What is the potential of additive manufacturing as a fabrication alternative to other processes? This guide is an introduction for those who want to explore the potential of ceramics as a 3D printing material. First, we’ll explain the fundamentals of ceramics in the following sections, and then we’ll proceed with 3D printing solutions.
What Do We Mean by Ceramics?
Most people would identify everyday household items as ceramics. We would guess the first things that come to mind is dishes, floor tiles, porcelain figurines, toilets and pottery. But not many people know that we can find ceramics almost everywhere. Common construction materials like bricks, cement and concrete are ceramics, many components on a car are ceramics, the device you’re using to read this article has ceramics, even the glass on your windows can be considered ceramics (We’ll get into that).
So, how do we define a ceramic? A ceramic is an inorganic non-metallic solid material that comes as the result of processing mineral compounds at high temperatures. Usually, these compounds are a combination of metallic, non-metallic and metalloid elements, mainly oxygen, carbon, nitrogen, silicon and boron. Some examples are alumina (Al2O3) found in refractory uses and carbon boride (B4C), one of the hardest materials in the world, used in cutting and abrasive tools.
Among its characteristic properties, ceramics in most cases are:
- Among the hardest, strongest and wear-resistant materials
- Thermal and electric insulators with high melting points (Ranging from 1000 C to 3000 C)
- Refractory, ideal for combustion chambers
- Inert and chemically stable, making them resistant to corrosion, combustion, acidic and alkaline substances, and potentially food-safe and biocompatible.
As a consequence of the above, these materials are also durable and ecologically friendly. On the other hand, however, ceramics tend to have disadvantages like:
- Brittleness or low toughness
- Susceptibility to thermal shocks
The key to their high mechanical performance lies in their crystalline structures due to the ionic and covalent bonds of their elements. However, the downside of these rigid bonds is that they lack the characteristic ductility of metals.
And, what about glass? Glasses are also inorganic non-metallic solids processed at high temperatures. The thing with glasses is that their structures are amorphous, in opposition to ceramic’s crystalline structures. Consequently, glasses have unique optical properties, glossy surfaces, low porosity and, thus, impermeability, however, at the cost of being more fragile. In reality, the line between these classifications blurs as crystallisation and vitrification processes enable a transition between glass and ceramic properties.
Types of Ceramics
Throughout history, the key ingredient for ceramic works has been natural clay. This material is abundant and easy to extract or mine from the earth crust. After mixing with water or agglutinants, this material gets its characteristic plasticity, which is friendly for craftsmen to form into desired shapes. Then, other minerals like kaolin, felspar, and quartz are added to achieve particular results to that same mix of clays. These ceramics are what we know as traditional ceramics.
The three main types of traditional ceramics are:
- Earthenware: The most basic type of ceramic. With its reddish-brown, opaque and porous appearance, an earthenware ceramic has low mechanical properties. However, earthenwares are affordable and easy to process with the lowest firing temperatures (Below 1200 C). This ceramic is commonly applied for affordable tableware and pottery uses, so it must be glazed to make it watertight.
- Stoneware: These greyish-brown ceramics with a distinct vitreous or semi-vitreous surface result from firing the clay at higher temperatures than earthenware (Around 1100 C to 1300 C). Although its uses are similar to earthenwares, their superior properties can be applied to some technical uses.
- Porcelain: Its white and glossy appearance is unmistakable. The secret lies in its key ingredient, kaolin, fired at even higher temperatures (Between 1200 C to 1400 C). Its aesthetically pleasing surface makes it ideal for premium tableware and pottery. But, getting beyond looks, porcelains have exceptional mechanical properties, which make them ideal for applications like sanitaryware, electrical insulators, spark plugs, cutting tools and strong building tiles.
Other uses for traditional ceramics are:
- Construction: Bricks and cement are also made out of ceramics. Regarding bricks, their earthy yet sturdy composition is a mix of clay and sand. On the other hand, the capacity to harden after reacting with water makes cement the most relevant and versatile building material today.
- Refractories: These are the essential components of high-heat processes like, for example, ovens that operate at elevated temperatures. Refractories are generally a mix of fireclay and high alumina.
Traditional ceramics, though archaic, remain whatsoever relevant to this day for their aesthetic value and effective technical uses. However, the advanced science of technical ceramics allows us to truly understand their applicability.
What is the main characteristic that sets apart technical from traditional ceramics? The answer is clay. Nowadays, technological advances enable manufacturers to synthesise powders, rather than clay, to form ceramics and push forward these materials’ true potential into endless possibilities. These ceramics performances have reliable performances in top-grade and demanding areas like the automotive, aerospace, medical and nuclear industries.
But the most attractive trait of these ceramics, we would say, is that they can defy the properties we previously defined for ceramic materials. For instance, some ceramics in the market, like lead oxide (PbO), have conductive properties, silicates are crucial for semiconductive materials in electronics, other ceramics are even superconductive, ferrites have magnetic properties, and ZTA toughness is exceptional. Thus, technical ceramics can be classified into two categories: Electro-ceramics and Structural.
- Electro-ceramics: The material of choice for electronic substrates, dielectrics, capacitors, insulators, conductors, magnets, piezoelectrics and optical applications like optic fibre cables; wherever properties of high resistivity, high heat resistance and durability are required.
- Structural: Many traditional metal parts can be replaced or coated with ceramics in high-performance mechanical applications thanks to their high heat resistance, wear-resistance and low reactivity. Some examples are motor and turbine components where thermodynamic efficiency can be improved with these. Some examples are space shuttle tiles, durable bits for CNC mills and reliable biomedical implants.
Ceramics are traditional yet highly technological materials, and the same goes for their production processes. Since these materials are versatile, there’re countless ways to deal with them, from homemade fabrication to extensive industrial facilities. There’re numerous aspects to the fabrication workflow of ceramics, but we’ll focus on those two essential for the scope of this article: Forming and sintering. Forming is the stage in which the material, whether it is clay or powder, gets its shape. Many established techniques make this possible, and among them, 3D printing is steadily taking its spot. After forming the material, the resulting object, the green object, is far from being functional nonetheless.
A sintering or firing process is required to form continuous crystalline structures across the object. The thing is that ceramics require extraordinarily high temperatures beyond 1000 C, so well-equipped kilns are needed. The sintering process is the heart of ceramics manufacturing, and almost everything revolves around it. For example, the part can shatter if moisture levels and air pockets aren’t properly controlled or if the mixture of raw materials has low quality. In short, implications in design constraints, handling of materials and their additives (Binders, plasticisers, anti-foaming), tolerances, and quality for each particular forming process emerge from this decisive firing process.
Now, how do these forming processes work? How would 3D printing be a legitimate alternative to these established methods? First, let’s have a brief view of the most common techniques.
- Slip Casting: In ceramics terminology, slip is the term for liquid clay. In a slip casting process, a two-part mould is filled with slip. In order to get a solid green part, this method requires the porous mould to be of a porous material, ideally plaster, to drain the excess liquid from the part. As this slurry dries, the resulting material accumulates in the cavity walls, leaving a shell with an increasing thickness. Slip casting is the most common ceramics industrial process due to its reliability and precision; however, it can take each mould more than 24 hours to complete the process.
- Pressure Casting: A variation of slip casting where porous polymeric moulds pressure the cast to achieve faster, multi-thickness and high-density results.
- Tape Casting: A laminating process to produce thin parts commonly used in printed circuits. The system consists of transporting with a conveyor belt thin layers of slip throughout a drying chamber. A doctor blade regulates the thickness of the laminate with a precision of microns.
- Injection Moulding: Virtually the same process as its polymeric counterpart, with similar pros and cons. In this case, ceramic powder is mixed with polymeric binders to achieve the desired flows. This method is commonly used for technical ceramics.
- Roller Tool Forming or jiggering: Similar to spinning wheel processes, but automatised. A spinning metal part forms the part until it gets its desired shape.
- Extrusion: The material is pushed through a die pattern. Typical applications are tubes, insulators, bricks, tiles and honeycomb structures for catalyst carriers.
- Dry pressing: It comprises the condensation of powders at high-pressure moulds. This process is ideal for shaping high-performance ceramics into parts with simple geometries like dielectric and magnetic components, refractories, grinding disks and tiles.
3D Printing for Ceramics Production
Unfortunately, established industrial ceramic forming processes rely on moulds exceedingly, which, as we know for polymers and metals, limit design freedom. Simultaneously, the upfront investment of most of these processes is costly, especially for injection moulding. So, the logical outcome of these challenges is adapting the digital workflows of 3D printing, which is ideal for prototyping and custom tooling.
And what about industries with low production and high customisation requirements like aerospace or electronics? What about the endless potential sprouting from the efficiency of 3D printed housing? As the development of these materials opens new possibilities, the demand throughout many industries, from pottery workshops to large scale production plants, grows.
Although it is not yet established as polymeric or metal additive manufacturing, ceramics 3D printing has been present for many years now, from desktop to industrial systems, and is becoming more relevant day by day. The leading 3D printing technologies are binder jetting, stereolithography, material extrusion and nanoparticle jetting.
As a pioneering system for metal additive manufacturing, binder jetting is also widely known for its capabilities for ceramics. In a similar fashion as other forming processes, this technology leverages the use of binding agents to join powder particles together, in this case selectively with an inkjet printhead. Similarly to an SLS process, a roller prepares a thin layer of powder for every layer aligning with the z-axis.
- Virtually any ceramic material can be printed with this process. Of course, with a proper adaptation of powders and binders formulae for the requirements of this process.
- No need for supports
- Complex geometries like lattice structures are possible
- Due to low compressions, the results mostly have high porosity, and thus low strength
- Not the best precisions
- Not the best surface finish
- Cleaning the powder after the printing cycle can be problematic for intricate geometries
Some of the companies leading this trend are ExOne and Voxeljet
Tho still in its infancy, the development of resins with ceramic suspensions is on a steady growth. In this case, the resin works as the binding agent after curating. Afterwards, the resin burns out as the ceramic particles densify during the sintering process.
- Great surface finishes
- Available in desktop format at affordable prices
- Potential for ceramic-polymeric composites
- Limited range of materials
- Particularly vulnerable to deformation and shrinkage during sintering
- Not as friendly as standard resins to print
Among its broad resin catalogue, Formlabs offers its own experimental ceramic suspension formula. This particular material is ideal for advanced mechanical prototypes, jewellery and fine arts. For more information, watch the following video or visit their page.
For high-scale industrial production, the 3DCeram is a notable company that offers ceramics photopolymerisation solutions.
Material extrusion or cold material deposition is a process akin to the FDM we all know: As an extruder pushes material through a nozzle, the printhead selectively deposits it layer by layer. However, the big difference that sets these two processes apart is the nature of the materials. While an FDM pulls and melts filament, a material extrusion printer plunges a clay or paste substance. Additional components like clay tanks, valves and air compressor might be needed to ensure the proper flow and rheology of the paste.
Extrusion results aren’t as compelling as other processes regarding resolution, layer heights, and mechanical performances. Consequently, this one is remarkably affordable compared to the other printing methods and reserved for desktop applications rather than industrial ends. 3D Potter and WASP are some of the ceramics extrusion 3D printing companies leading this trend.
The company XJet developed its own patented technology, Nanoparticle Jetting, which leverages the material jetting (Polyjet) mechanism for metal and ceramics printing. Just as other material jetting technologies, Nanoparticle Jetting uses two sets of photocurable inks: The build material and the soluble support. However, the core innovation here is that the build material is a liquid dispersion of ceramics nanoparticles in a binding substance. Each droplet deposits several material particles during the printing process while the liquid evaporates due to high temperatures. The results are dense parts, which is integral for optimal performance and low sintering shrinkages. And, just as we know from material jetting in general, this process has exceptional resolutions, precision and manufacturability.
This company offers two dedicated models for ceramics additive manufacturing: The XJet Carmel 1400 and the XJet Carmel 700.
The Future of Ceramics 3D Printing
The consulting company for additive manufacturing, SmarTech Analysis, released its 2019-2030 forecast report offering a comprehensive view on the promising future of ceramics 3D printing production. According to this report, ceramics 3D printing is increasingly becoming a standard in several industries and maturing from a prototyping technology to serial part production and marking 2025 as the inflexion point for this evolution.
Among its many aspects, this document presents the most important additive manufacturing technologies, materials, market forecasts, industry leaders, applications, and potential adopters. For more information on this analysis, click here.
As it happens for ceramics, 3D printing is the future for several more applications for business and daily life, and SolidPrint3D is here to help you make the best decisions to invest in this future. For more information, please call SolidPrint3D on 01926 333 777 or email on firstname.lastname@example.org.
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