Production technology of precoated sand for selective laser sintering and quick molding technology

Abstract

The invention discloses a production technology of a precoated sand for a selective laser sintering and quick molding technology. The formula of the precoated sand comprises the following components: crude sands, a binding agent, a curing agent, a lubricant, and an addictive; wherein the crude sands are selected from a foundry sand with a particle size of 100 to 200 meshes, the binding agent is selected from a PF-1904 thermoplastic solid phenolic resin whose melting point is from 80 to 90 DEG C, the curing agent is selected from white or colorless crystal urotropine powder, the lubricant is selected from white calcium stearate powder, and the addictive is selected from silane colorless transparent liquid coupling agent KH-550. The production technology of the precoated sand for the selective laser sintering and quick molding technology adopts a fine and round foundry sand, selects a resin with a low melting point, reduces the addition amount of the resin, strictly controls the temperature when the binding agent and the curing agent are added, and adds a proper amount of addictive so as to manufacture a high strength and low gas evolution precoated sand, which is suitable for the selective laser sintering and quick molding technology.

Description

technical field [0001] The invention relates to the field of production technology of coated sand, in particular to a production technology of selective laser sintering rapid forming coated sand. Background technique [0002] Selective laser sintering rapid prototyping technology (SLS for short) is a new casting technology that directly sinters powder materials into various solid shapes by laser. Coated sand is one of the powder materials used in selective laser sintering rapid prototyping technology. Laser sintering rapid prototyping technology is a technology in which the phenolic resin is heated by laser to soften and solidify, so that the coated sand is bonded to form a sand core. This new forming technology does not require molds, is suitable for new product development, shortens the development cycle, and is conducive to reducing the time cost and economic cost of mold modification. [0003] The traditional hot box core making method is to fill the coated sand into t...

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Problems solved by technology

[0014] 2. The particle size of the original sand is 50 / 100 or 70 / 140. The coarser the original sand, the thicker the powder layer thickness allowed in SLS, which is not only easy to produce step effect, which is not conducive to improving the surface quality of SLS sand core, but also There will be obvious delamination phenomenon, and the adhesion between layers is not enough, which will easily cause SLS forming failure

[0015] 3. The amount of binder that is phenolic resin added reaches 3-6%. Although the resin content is higher, the strength of the sand core is better, but the amount of gas generation is correspondingly larger, which is unfavorable for the pouring of the sand core.

[0017] 5. Due to the production process of the traditional hot box method, the coated sand for core making cannot be stored for too long, and it is easy to agglomerate, which will reduce the strength of the coated sand and cannot be formed smoothly during sintering

The coated sand used for core making by the traditional hot box method is not suitable as a laser due to the shortcomings of large particle size of the original sand, irregular shape, large amount of resin added, large gas generation, and high melting point of the resin, which leads to bonding of unsintered coated sand. Sintering powder materials for rapid prototyping

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