Mold Shape Density And Shrinkage Rate

As the obvious advantages in higher quality,lower rejection rate andnon-overlapand and so on, the LFC develops rapidly and more and moreenterprise have been built recently.But the lack of the related theory on LFCto guide the production, many companies can not stabilize production steady andmay collapse soon,causing great economic loss. LFC patterns is one of the keyto the success of Lost Foam Casting, and some basic research aiming at thepreparation of LFC will be studied in this article.Two key indicators affecting the quality of LFC pattern are the density andshrinkage rate.Too large pattern density affects the filling of liquid metal andmakes it prone to defect in castings.Too small pattern density, of which thestringency is not enough, results deformation and quality defects on castingsurface. How to balance the contradiction between the two in the moldingprocess has became the problem we must consider.The shrinkage of LFC effectsthe shrinkage of disappear casting mold shape.And too large shrinkage willmake the casting scraped. Based on this, this paper studies Adopting vacuumprefoaming and the shape foaming with vertical foam model machine. It is teston effective influence caused to the density and shrinking of expandablepolystyrene(EPS),copolymer(STMMA)pattern researched cocerning prefoamingand foaming process; on the basis of it, By observating the surface roughness ofpatterns, analysising the process factors on the the surface roughness of EPSgrinding balls patterns, obtaining the following conclusions.（1）Pattern density decreases with the extension of pre-expandable time,molding time and ripening time, the increase of molding steam pressure. Theeffect of pre-expandable time on the pattern density are greatest, molding steampressure and molding time,the effect of ripening time on the pattern density.（2）Pattern shrinking decreases with the extension of pre-expandable timeand ripening time, the increase of molding steam pressure.The effect of moldingsteam pressure on the pattern shrinking are greatest, pre-expandable time followed by molding steam pressure, the effect of ripening time on the patternshrinking, storage temperture on the overall shrinking has no effect.The totalshrinkage rate of expandable polystyrene is about0.6%~0.7%, The totalshrinkage rate of copolymer is about0.2%~0.35%.(3) It is tested by experiment that pre-expanding time is the biggest influencefactor on the grinding balls pattern density. molding steam pressure and moldingtime,the effect of ripening time on the pattern density. Optimal conditions forexperimental conditions: pre-expandable time is nine minute, molding steampressure is0.1MPa, molding time is14s, ripening time is4h.