vacuum casting and lost foam casting is also called negative pressure casting. the biggest difference between Vacuum casting and traditional sand casting is that Vacuum casting don’t need binder.
Vacuum casting uses plastic film to seal up molding flask ,then , drawing-off air from mold by vacuum pumping system , pressure difference has been formed and makes dry sand closely knit , the needed cavity has been taken shape . Through core setting , mold assembling , pouring and vacuuming supply ,make the casting curdle , remove negative pressure ,next , the casting will be acquired with the molding sand scattering.
The advantages of vacuum casting : firstly , because it adopts negative pressure , so , the sand holes and air holes less , high compactness , surface smooth and bright , edge sharpness and size accurate ; secondly , energy conservation , efficient and cleaner production , dry sand can be repeatedly used because of no binder , the coal consumption reduces and power consumption increases , but ,it is broadly reducing the dust and noxious gas and saves the human resources ; in addition , Vacuum casting can also increase of the casting service life and is well thought of the user , becomes a new favorite in foundry industry.
Vacuum casting also called vacuum moulding or vacuum sealed molding, which is invented by the Japanese as a new molding process in seventy’s of the last century .It is the third generation of modeling process without binder ,namely physical modeling method.vacuum casting has got rapid speed of development in recent years because of its good appearance quality of castings and low running cost.
The basic operation principle of vacuum casting is to filled anhydrous quartz sand without binder in special sand box.Then we can get the casting after sealing the sand box with plastic film and vacuumizing it to make the casting mold without binder sand compacted and molded by the differential pressure inside and outside of the casting.
Castings produced by vacuum method have not only good quality , smooth surface, high dimensional precision , but also low comprehensive cost. Though the vacuum casting method make use of disposable plastic film, the sand mould without binder ,high recovery rate and low cost of casting cleaning have reduced the machining allowance and improved labor productivity. The cost of vacuum castings is lower than hardening sand, sodium silicate sand and tidal sand mold.