Cavitation and Bubble Dynamics: Preface

Binder Jet printing is an additive manufacturing technique that dispenses liquid binding agent on powder to form a two-dimensional pattern on a layer. The layers are stacked to build a physical article. Binder Jetting (BJ) can be adapted to almost any powder with high production rates and the BJ process utilizes a broad range of technologies including printing tehniques, powder deposition, dynamic binder/powder interaction, and post-processing methods. A wide variety of materials including polymers, metals, and ceramics have been processed successfully with Binder Jet. However, developing printing and post-processing methods that maximize part performance is a remaining challenge. This article presents a broad review of technologies and approaches that have been applied in Binder Jet printing and points towards opportunities for future advancement.

Binder jetting: A review of process, materials, and methods

Binder jet 3D printing—Process parameters, materials, properties, modeling, and challenges

In recent years, Additive Manufacturing (AM), also called 3D printing, has been expanding into several industrial sectors due to the technology providing opportunities in terms of improved functionality, productivity, and competitiveness. While metal AM technologies have almost unlimited potential, and the range of applications has increased in recent years, industries have faced challenges in the adoption of these technologies and coping with a turbulent market. Despite the extensive work that has been completed on the properties of metal AM materials, there is still a need of a robust understanding of processes, challenges, application-specific needs, and considerations associated with these technologies. Therefore, the goal of this study is to present a comprehensive review of the most common metal AM technologies, an exploration of metal AM advancements, and industrial applications for the different AM technologies across various industry sectors. This study also outlines current limitations and challenges, which prevent industries to fully benefit from the metal AM opportunities, including production volume, standards compliance, post processing, product quality, maintenance, and materials range. Overall, this paper provides a survey as the benchmark for future industrial applications and research and development projects, in order to assist industries in selecting a suitable AM technology for their application.

Advances in Metal Additive Manufacturing: A Review of Common Processes, Industrial Applications, and Current Challenges

During the additive manufacturing (AM) process, energy is transferred from the energy beam to the processed material. The high-energy input and uneven temperature distribution result in the high-temperature gradient, large thermal stress, and warping deformation. The scanning strategy, one of the representative AM processing parameters, plays an important role in the microstructures, mechanical properties, and residual stresses of 3D printed parts. It is necessary to review the current state of research about scanning strategy in additive manufacturing, and this paper seeks to address this need. This review mainly focuses on the scanning strategies in selective laser melting process. Various scanning strategies and their effects on mechanical properties, microstructures, and residual stresses of selective laser melted parts are summarized. Finally, some suggestions on the optimization of scanning strategy for better performance are provided based on the above analysis.

https://link.springer.com/content/pdf/10.1007/s00170-021-06810-3.pdf

Scanning strategy in selective laser melting (SLM): a review

Effect of laser energy density on the microstructure, mechanical properties, and deformation of Inconel 718 samples fabricated by selective laser melting

Effects of hollow structures in sand mold manufactured using 3D printing technology

The advance of additive manufacturing drives the design of molds for castings. In the present study, a type of skeletal mold for castings was proposed, which includes two structures, lattice-shell and rib enforced shell. The shell forms the cavity for a casting and the surrounding ribs or lattices support and enforce the shell. This type of mold structure design results in fast and uniform cooling of a casting, which can improve production efficiency and reduce the deformation and residual stress of a casting. In addition, it provides more space and flexibility to adjust the cooling conditions of interested locations of a casting. The thickness of the shell can be varied according to the local geometries of a casting. The support is designed based on the hydrostatic pressure before solidification and the weight after solidification. An air pocket (hollow structure) in the shell was designed for the riser to postpone its solidification and then facilitate shrinkage feeding. The experimental results revealed that the new design of sand molds saved at least 60% sand and shortened the shakeout time by at least 20%. Local hollow structure prolonged its solidification process by approximately 15%.

Additive manufacturing-driven mold design for castings

A rib-enforced shell mold for castings is proposed to replace the traditional dense mold. The 3D printing methods of sand mold make this new mold design a reality. The rib-enforced shell mold has been applied to cast a stress frame specimen of Al alloy A356. The effects of rib-enforced shell sand mold and traditional dense mold on the cooling of this casting have been investigated and compared. The results show that the cooling efficiency of the casting increases significantly by using rib-enforced shell mold, and approximately 40% cooling time is saved in natural condition and 35% further is saved in air blowing condition for the stress frame specimen before shakeout. This mold makes it possible to adjust the cooling condition of interested locations. It ensures fast and uniform cooling of the casting which can improve production efficiency and reduce deformation and residual stresses of the casting. Temperature distribution in the rib-enforced shell sand mold during the solidification was measured by an infrared imaging camera. The produced casting has good dimensional accuracy and surface quality. Meanwhile, nine-tenths of the sand is saved per mold.

3D-printed rib-enforced shell sand mold for aluminum castings

Ultrasonic treatment of the melt metals is a hot research topic; however, it is hard to introduce ultrasound into liquid steel because of the requirement of resistance to high temperature and erosion in the melt. In this paper, the author proposed a new method to introduce ultrasound into liquid steel. The metal to be treated is cast together to the tip of the booster. During the test, the booster is placed upward with the metal to be treated connected on the top as a free end, which is melt by induction coils. The booster which generates ultrasound, by this way, acts on the melt pool. The determination of the length of the booster under this situation is given. The effect of ultrasonic treatment on the melt of 304 stainless steel is studied. The microstructure of the treated area is significantly refined and equi-axed grains are obtained; the fragmentation of inclusions occurs due to the ultrasonic treatment; the mechanism of the fragmentation of the dendrite and inclusions is discussed.

/pdf/ultrasonic-treatment-of-the-304-stainless-steel-melt-55j46o8bf1.pdf

Yongyi Hu

Papers

Effect of laser energy density on the microstructure, mechanical properties, and deformation of Inconel 718 samples fabricated by selective laser melting

Effects of hollow structures in sand mold manufactured using 3D printing technology

Additive manufacturing-driven mold design for castings

3D-printed rib-enforced shell sand mold for aluminum castings

Ultrasonic Treatment of the 304 Stainless Steel Melt