Effect of sand-mold material and extrusion forming process on sand-mold surface properties

Considering the digital flexible extrusion sand mold as the research object, the surface quality of sand mold was studied by designing a single-factor experiment, and then the optimal parameter for the high-precision flexible forming of sand mold was obtained. The results show that there are differences in surface properties between the outside and inside of the sand mold, and the different types of sand mold had different surface properties. The angle coefficient of sand has a great influence on the sand mold surface properties. With the increase in the extrusion force, the distance between sand grains decreases and the parallel connection mode of sand grains increases. When the sand mold was cut, the number and extension depth of cracks of the sand mold were greatly reduced; thus, the sand mold surface properties increased. With the increase in the resin content, the coating thickness of sand grains increases, the bonding bridge of sand grains increases, the sand mold strength increases, the number of cracks of sand mold decreases, and the surface properties of sand mold increase. In this paper, a new method to obtain the surface quality of sand mold is provided, which can help popularize the precision forming technology of pattern-less casting. The method of sand-mold near-net forming with digital flexible extrusion makes the extrusion unit array pack form the sand-mold cavity. Moreover, in the digital precision forming technology without pattern casting, by filling the mold with molding sand, holding pressure, and hardening, the sand-mold near-net forming is obtained as a preform. This technology saves a lot of molding sand and reduces the amount of cut molding sand in the process of the digital precision forming technology without pattern casting. As the preliminary process of the sand-mold digital precision forming without pattern casting, the technology of sand-mold near-net forming with digital flexible extrusion effectively shortens the development cycle of castings. The basic research on sand mold efficiently achieves high-quality and near-net forming of sand molds with digital flexible extrusion. The research improves the digital level, eco-friendliness, and efficiency level of pattern-less casting technology.