Leu-M

Additive manufacturing (AM) technology has been researched and developed for more than 20 years. Rather than removing materials, AM processes make three-dimensional parts directly from CAD models by adding materials layer by layer, offering the beneficial ability to build parts with geometric and material complexities that could not be produced by subtractive manufacturing processes. Through intensive research over the past two decades, significant progress has been made in the development and commercialization of new and innovative AM processes, as well as numerous practical applications in aerospace, automotive, biomedical, energy and other fields. This paper reviews the main processes, materials and applications of the current AM technology and presents future research needs for this technology.

Additive manufacturing: technology, applications and research needs

Along with extensive research on the three-dimensional (3D) printing of polymers and metals, 3D printing of ceramics is now the latest trend to come under the spotlight. The ability to fabricate ceramic components of arbitrarily complex shapes has been extremely challenging without 3D printing. This review focuses on the latest advances in the 3D printing of ceramics and presents the historical origins and evolution of each related technique. The main technical aspects, including feedstock properties, process control, post-treatments and energy source–material interactions, are also discussed. The technical challenges and advice about how to address these are presented. Comparisons are made between the techniques to facilitate the selection of the best ones in practical use. In addition, representative applications of the 3D printing of various types of ceramics are surveyed. Future directions are pointed out on the advancement on materials and forming mechanism for the fabrication of high-performance ceramic components.

3D printing of ceramics: A review

Materials for additive manufacturing

This paper offers a review of present achievements in the field of processing of ceramic-based materials with complex geometry using the main additive manufacturing (AM) technologies In AM, the geometrical design of a desired ceramic-based component is combined with the materials design In this way, the fabrication times and the product costs of ceramic-based parts with required properties can be substantially reduced However, dimensional accuracy and surface finish still remain crucial features in today's AM due to the layer-by-layer formation of the parts In spite of the fact that significant progress has been made in the development of feedstock materials, the most difficult limitations for AM technologies are the restrictions set by material selection for each AM method and aspects considering the inner architectural design of the manufactured parts Hence, any future progress in the field of AM should be based on the improvement of the existing technologies or, alternatively, the development of new approaches with an emphasis on parts allowing the near-net formation of ceramic structures, while optimizing the design of new materials and of the part architecture

Additive Manufacturing of Ceramic‐Based Materials

A novel, environmentally friendly solid freeform fabrication method called freeze-form extrusion fabrication (FEF) has been developed for the fabrication of ceramic-based components. The method is based on deposition of ceramic pastes using water as the media. The ceramic solids loading can be 50 vol.% or higher and initial studies have focused on the use of aluminum oxide (Al2O3). The FEF system components and their interaction are examined, and the main process parameters affecting part geometry defined. Three-dimensional shaped components have been fabricated by extrusion deposition of the ceramic paste in a layer-by-layer fashion. The feasibility of this process has been demonstrated by building components having a simple geometry, such as cylinders and solid or hollow cones. Hollow cones have also been fabricated to demonstrate the ability to build structures with sloped walls.

Freeze-form Extrusion Fabrication of Ceramic Parts

Purpose – The purpose of this paper is to develop an inexpensive and environmentally friendly solid freeform fabrication technique, called the freeze‐form extrusion fabrication (FEF), and use this technique in advanced ceramic fabrication.Design/methodology/approach – FEF uses a highly loaded aqueous ceramic paste (≥50 vol.% solids loading) with a small quantity (∼2 vol.%) of organic binder to fabricate a ceramic green part layer by layer with a computer‐controlled 3D gantry machine at a temperature below the freezing point of the paste. Further, a freeze‐drying technique is used for preventing deformation and the formation of cracks during the green part drying process. Following the freeze‐drying, the ceramic green part undergoes binder removal and is sintered to near full density.Findings – Extrudable, alumina pastes of high solids loading and process parameters for FEF processing of these pastes have been developed. Paste rheological properties and stability, extrusion rate, 3D gantry motion speed and...

Aqueous‐based freeze‐form extrusion fabrication of alumina components

Aqueous-Based Extrusion of High Solids Loading Ceramic Pastes: Process Modeling and Control

Aqueous-Based Extrusion Fabrication is an additive manufacturing technique that extrudes ceramic slurries of high solids loading layer by layer for part fabrication. The material reservoir in a previously developed system has been modified to allow for starting and stopping of the extrusion process on demand. Design pros and cons are examined and a comparison between two material reservoir designs is made. Tests were conducted to determine the optimal deposition parameters for starting and stopping of the extrudate on demand. The collected test data is used to create a process model that describes the relationship between ram velocity and material extrusion rate. This model allows for the development of a deposition strategy that improves material deposition consistency, including reduced material buildup at sharp corners. Example parts are fabricated using the deposition strategy and hardware design. INTRODUCTION Aqueous based extrusion fabrication (ABEF) of ceramics is a Solid Freeform Fabrication (SFF) process that deposits ceramic paste layer by layer through extrusion. The process has been previously introduced, and details regarding the build material and equipment can be found in [1-3]. A process schematic and photograph are shown in Figures 1 and 2 respectively. The material deposition device previously developed gave good results for continuous material deposition. The ability to start and stop the material extrusion on demand was not yet developed in our previous work. With the need to be able to fabricate more complex geometries, different extrusion processes were surveyed for the process of starting/stopping material deposition on demand. The first system surveyed was the Fused Deposition of Ceramics (FDC) process, which modified a Fused Deposition of Materials (FDM) machine to deposit a ceramic/polymer fiber strand [4-5]. The FDM process uses two rollers with heaters to move the material fiber either forward for deposition or in reverse to stop the deposition. The second process uses a the Micro-Scale Robotic Deposition System [6]. This process uses air pressure to extrude material for deposition and uses one-way control valves for starting and stopping of the extrusion process. These “retraction” processes can be applied to the ABEF system by retreating 1

Aqueous-based extrusion fabrication of ceramics on demand (preprint)

A novel, environmentally friendly solid freeform fabrication method called Freeze-form Extrusion Fabrication (FEF) has been developed for the fabrication of ceramic-based components. The method is based on deposition of ceramic pastes using water as the media. The ceramic solids loading can be 50 vol. % or higher and initial studies have focused on the use of aluminum oxide (Al2O3). The FEF system components and their interaction are examined, and the main process parameters affecting part geometry defined. 3-D shaped components have been fabricated by extrusion deposition of the ceramic paste in a layer-by-layer fashion. The feasibility of this process has been demonstrated by building components having a simple geometry, such as cylinders and solid or hollow cones. Hollow cones have also been fabricated to demonstrate the ability to build structures with sloped walls.

Michael S. Mason

Papers

Freeze-form Extrusion Fabrication of Ceramic Parts

Aqueous‐based freeze‐form extrusion fabrication of alumina components

Aqueous-Based Extrusion of High Solids Loading Ceramic Pastes: Process Modeling and Control

Aqueous-based extrusion fabrication of ceramics on demand (preprint)

Freeze-Form Extrusion Fabrication of Ceramics