1.Put appearance on a medium –altitude mould board，there is some spiracle in the appearance， at the role of the，these spiracle is used for making plastic film close to the appearance.
Use the calorifier to heat and soften the plastic film which has big elongation，heating temperature is 80～120℃.
3. Film shaping
Soften thin film is covered on the surface layer of appearance，through the air hole， under the pull of cast vacuum 200～400mmHg ，make thin film close to the surface of model.
4. Place of sand box
After spraying paint and drying，put the sand box on the model which is covered with thin film.
Open pouring cup ，slick surface of sand body，coat plastic film，in order to close sand box.
6.Mould assembling casting
Core setting and chilling block according to requirements of technology before mould assembling.
7. Drawing shakeout
After suitable cooling time cancel cast vacuum and recover atmospheric pressure state, make free- mobility sand outflow，leave clean casting without sand lump and burnt-in sand.
The passage above talks about parts of the process of cast vacuum.