提高空心叶片铸型精度的光固化原型内腔结构设计方法

摘要

Stereo lithography (SL) prototype was used during the fabrication of integral ceramic mold for hollow turbine blade. The ceramic shell generally cracked due to the mismatch of the thermal expansions between the SL prototype and the shell as the prototype was burnt out. To solve the problem,the SL prototype was usually designed to thin-walled hollow parts with one size. However,the root of the SL prototype would deform due to the static pressure during the gel-casting process for fabricating large ceramic mold,resulting in a poor accuracy of the ceramic mold. A method of designing the SL prototype to thin-walled hollow parts with two different sizes was proposed. The sizes of blade rows and roots were 0.7 mm and 0.9 mm respectively by finite element analysis of the structural stiffness of prototype blade and the thermal structural strength of mold. CT and reverse precision analysis showed that the optimized design can decrease the deformation of the prototype root. The large size ceramic mold of hollow blade with high accuracy and complete structure was fabricated at last.%在空心涡轮叶片型芯型壳一体化陶瓷铸型制备过程中,对光固化叶片原型进行整体式内腔结构设计,可显著降低原型烧失过程中铸型的热应力,避免型壳开裂. 但在大尺寸叶片铸型的凝胶注模成形过程中,叶片原型榫根部位因刚度偏低,在陶瓷浆料静压力作用下会变形,导致铸型精度较差. 为此,提出了一种原型分区域内腔结构设计方法,并基于叶片原型静压力结构刚度-铸型热结构强度有限元模拟, 确定了叶身和榫根部位分别采用0.7 mm和0.9 mm的内腔结构尺寸.采用工业CT及逆向精度分析比较了分区域内腔结构设计前后铸型的精度变化,结果表明:分区域内腔结构设计方法降低了凝胶注模过程中原型榫根部分的静压力变形,有效改善了铸型的整体精度,避免了脱脂过程中铸型开裂,可制备出精度高、结构完整的大尺寸叶片陶瓷铸型.