Study And Application On The Cast Material Of Crack Resistance Gypsum Mould And Equal Wall Thickness Of Cast Mould

The gypsum mould casting is an especial cast process. Integrate thin-walled, complex and non-shaving precision casts can only be produced by this process. The casts made by gypsum mould casting are characterized by fine surface, good size and shape precision. Recently, the technology of gypsum mould cast and RP have combined. It provides a way for that cast moulds design and manufacture rapidly, and heighten the flexibility of cast produce. But the inherent disadvantages of gypsum mould restrict development of the technology. The blend powder that the gypsum mould slip cast used can use only one time, so it wastes resource too much. The traditional baked time exceed sixty hour, so the efficiency is very low and wastes of energy sources. These shortcomings limited the use popularization of the gypsum mould slip cast.In view of the flaws which exist in the traditional gypsum mould slip cast. The variable volume flask and the blocks are designed, and equal-thickness wall of the gypsum mould is realized through the change of flask volume and assembling blocks. Heat conduction material A is joint into the gypsum mould powder and the formula of gypsum mold powder is improved, the overall performance of the gypsum mold is enhanced. Combination traditional process of gypsum mould slip casting and the results of experiments, the thesis optimizes the baked curve and formulates the integrity process of the equal-thickness wall gypsum mould cast. The central achievements in the thesis are:①Designed variable volume flask. Based on the wax parts volume between 400×300×300mm and minimum 50×50×50mm, a variable volume flask are designed and manufactured, the flask can be adjusted itself size to adapt the best volume of the wax parts.②Designed a series of standard blocks. In order to realize equal-thickness wall of gypsum mould. The blocks are introduced in gypsum mould slip cast the first time. In accordance with the actual shape characteristics of parts, the thickness of gypsum mould approximately equal to about 20mm can be made through using different assemblage of mould.③In order to enhance the strength of gypsum mould, improve thermal shock resistance of gypsum mould and reduce the possibility of the collapse of gypsum mould, fiberglass was added in gypsum blend powder as filler. ④Because the thermal conductivity of gypsum mould is poor, it has affected the baking process and the casting process of gypsum mould. Therefore, a thermal conductivity material A is joint. After joining thermal conduction material A, the thermal conduction capacity and thermal shock resistance of gypsum mould are greatly enhanced, and the expansion rate minishs along with the joined quantity .Otherwise the intensity of gypsum mould is changed little, and it can fully achieve the requirements of gypsum mould slip casting.⑤Through a series of experiment to research crystal transformation of gypsum at various temperatures and the performance change of other components in gypsum blend powder in the baking process. Combined with the performance of equal-thickness wall gypsum mould in experiments, a practical value baking process parameters are obtained.⑥Through the research of the performance of equal-thickness wall gypsum mould, an integrated equal-thickness wall gypsum mould process is draw up, and the industrial costs of the new gypsum mould slip cast process has been compared with the costs of traditional gypsum mould slip cast.It can improve productivity and realize the purpose of saving materials and energy that produce casting as equal-thickness wall gypsum mould slip cast process. It has good economic efficiency and the great significance to the gypsum mould slip cast.