In recent years, molds for casting formed by 3D additive manufacturing (AM) technology are being increasingly applied to prototypes and molds for small-volume production. Technical development aiming for mass production in the future is underway using advanced AM technologies and casting technologies. Mass production is expected to improve the potential of the whole mold, including realization of more complex internal structures and thinner and lighter products due to improved accuracy of cavities. To meet these requirements, a government project was launched to develop a high-speed 3D AM technology that uses a commercialized large machine to perform high-speed recoating using solid catalyst coated sands which helps realize high fluidity. However, the 3D AM sand molds made by this process are thrown away rather than being reclaimed after casting, as are the furan AM sand molds made with printers from overseas. On the other hand, most of the molds made by current mainstream molding methods are reprocessed and used as reclaimed sand.

  Considering environmental and economic considerations, it is preferable to recycle the molds after the molding process to reclaim the sand. However, recycling is difficult due to the fine particle size, which makes mechanical recycling by rubbing the sand against each other physically difficult. Thus, in this study, we attempted to dismantle a 3D AM sand mold after casting to reclaim sand, then heat the sand and thermally decompose the binder hardening material attached to the sand surface to produce reclaimed sand with a Loss on Ignition of approx. 0.0%. The reclaimed sand was found to have a Loss on Ignition of about 0.0 %, as well as to contain calcium of alkali earth metals and sodium and lithium of alkali metals due to chemical transformation on some parts of the sand surface. Moreover, the compound resulting from the bonding of these elements was found to reduce the ability of the acid catalyst to harden the furan binder sand, making the reclaimed sand unusable with methods that manufacture coated sad using new sand and solid catalyst. As a new solid catalyst for coated sand, we used methanesulfonic acid with high catalytic activity together with conventional metaxylene sulfonic acid to coat sand with anhydrous magnesium sulfate to both neutralize alkaline substances and ensure catalytic activity as well as fluidity, and successfully developed a new solid catalyst coated sand. As a result of performing 3D AM experiments using the new solid catalyst coated sand, the AM results were found to be as good as that using solid catalyst coated sand made of new sand.

  Green sand is controlled by the properties of green sand test piece ; which is usually made by the ramming method. In recent years, machine molding by squeeze compacting instead of ramming has become the established method for the green sand molding process. Also there are concerns about the influence of making methods of test piece and sand types on the green sand properties.

  In this study, green sand test piece was made by changing the making method, squeeze pressure, squeeze speed, and types of sand using three types of test piece making equipment. The bulk density, permeability, and mold strength were measured as static properties. The experiment results obtained showed that the static properties are influenced by the differences between the ramming and squeeze methods, squeeze conditions, diameter of sand, and grain distribution of sand.

  For reason, the relationship between the squeeze pressure and height of sand layer during test piece making was investigated as dynamic compacting behavior. Two mechanisms of dynamic compacting behavior were seen : rearrangement of particles and visco-elastic deformation of the bentonite layer. These relationships were also influenced by how the test piece is made like static properties.

  The heat transfer coefficient (HTC) between molten alloy and mold is essential for conducting filling and solidification analysis of the casting process. It is known that the HTC depends on the contacting condition between the solidifying alloy and mold. The objective of this study is to obtain and compare the HTC under different contact conditions using the temperature histories of a cylindrical furan sand mold and aluminum alloy, JIS AC4CH (A356). The finite difference method was used to estimate the temperature differences between the alloy and mold. As a result, differences in the HTC were confirmed between the bottom and side directions of the mold. Furthermore, it was found that the HTC changed during solidification from liquidus temperature to the completion of eutectic solidification. This demonstrates that the HTC depends on the contacting pressure between the solidifying layer and mold.