Coated sand for selective laser sintering (SLS) and preparation method thereof

Abstract

The invention discloses coated sand for selective laser sintering and a preparation method thereof. The coated sand comprises crude sand, a compound binder, a curing agent, a lubricating agent and a light absorber, wherein the compound binder comprises phenolic resin and epoxy resin; the curing agent is formamine; the lubricating agent is zinc stearate, calcium stearate or lithium stearate; and the light absorber is carbon black. The preparation method comprises the following steps: firstly, carrying out freeze grinding on the epoxy resin; then selecting epoxy resin powder with suitable particle size distribution by a sieving method; and finally, evenly mixing a certain ratio of epoxy resin powder, the carbon black and phenolic resin coated sand prepared by the existing process. Due to the fact that the strength of the SLS formed part of the coated sand is higher, the coated sand can be used for SLS of casting sand moulds (cores) with large-size and complicated structures.

Description

technical field [0001] The invention belongs to the field of new materials, in particular to a coated sand used for selective laser sintering (SLS) forming and a preparation method thereof. technical background [0002] SLS technology is a rapid prototyping technology (rapid prototyping, RP) that uses laser as a heat source to sinter powder materials. , the solid powder material is directly formed into a three-dimensional solid part, which is not affected by the complexity of the formed part. [0003] SLS technology can directly prepare sand molds (cores) for casting, from part drawings to process design of molds (cores), and three-dimensional solid modeling of molds (cores), etc. are all completed by computers. Especially for some curved surfaces or runners in space, it is very difficult to form them by traditional methods. If SLS technology is used, this process will become very simple, because it is not limited by the complexity of the parts. When preparing large-size s...

AI Technical Summary

Problems solved by technology

[0005] However, the existing phenolic resin coated sand and its preparation process are all developed for traditional forming methods, not for SLS forming technology

The existing problems are: the strength of the existing SLS molded parts (before post-curing) of phenolic resin coated sand is low, and some fine structures are easily damaged in post-treatment processes such as powder cleaning and transfer, and large-sized molded parts are more likely to break

The main reasons for the low strength of SLS formed parts of phenolic resin coated sand are: different from traditional heating and curing forming, the time of beam irradiation and heating during laser scanning forming is very short, and the thermal conductivity of coated sand is small, which is As a result, the phenolic resin is not cured and cross-linked in some areas in the single layer and the layer-to-layer bonding area, and the sand particles are only bonded by the softening of the phenolic resin. However, the interface between the phenolic resin and the sand is poorly bonded, which causes its SLS to form The strength of the piece (before post-curing) is low