Manufacturing – Casting methods - European Aluminium Association

1.8.2 VDC Process
Vacuum Dies
The principle of vacuum die casting requires the dies to be very tight. Residual pressure is as
low as 20 - 30 hPa. (Normal atmospheric pressure is 1013 hPa). Therefore tools consist of
frames and one or several inserts with air seals in between. Good quality tools loose less than
1.5 hPa/s of vacuum.
Melt
The melt is kept in the dosage furnace below the filling chamber. Melt cleanness determines
heat treatability as well as weldability of castings. If the gas content is too high, heat treatment
produces humps on the surface, also called blisters.
Vacuum Die Casting Step 1: Dosage
In this step the low air pressure in the filling chamber sucks a portion of melt into the filling
chamber. The amount of metal can be adjusted.
1. Step: Dosage, suction of metal into the feeding chamber
Source: Müller-Weingarten
2. Metal Transport:
The piston drives up and seals the suction pipe. The melt is pressed to the gate. Metal
velocity in this phase is low.
2. Step: Transport of metal to the gate
Source: Müller-Weingarten
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