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Aluminum Alloys

Low-pressure aluminum casting machine with handling robot, peripheral equipment and materials-handling technology

Compared to gravity casting, low pressure casting offers following advantages: In low pressure casting, the metal within the furnace is pressed through the riser tube into the mould by pressure which works on the metal surface (picture 1).This form of mould filling is the most important difference to gravity and tiltabe casting. The process of mould filling proceeds absolutely controlled. This results in a low-turbulence or even turbulence-free mould filling.

The metal within the furnace is in a closed vessel under protected atmosphere. As a result, the melting absorbs less hydrogen and other impurities and the formation of oxide films is reduced. This is the basis for good melting quality.

Unlike in gravity casting, the metal surface is not continuously interrupted by re-dosing in low pressure as the melting is removed through the riser tube under the metal surface. The result is again clean metal. Especially process sections like the filling of the mould are repeatable executed directly by the machine and therefore depend no longer on the day's form of the "foundryman with the ladle". Moreover, operator errors can be minimized by automated process.

One of the major advantages of low pressure casting is the smaller gating system compared to gravity casting. Feeders are normally not necessary (head feeders only in the minority of cases) which reduces the cycle material. In low pressure casting, cycle material is 5 % to 20 % of casting weight whereas in gravity casting it can be up to 100 %. Less gating material also means that costs for cleaning, trimming and melting-down can be reduced significantly. Costs for cleaning are mainly personnel costs, especially for jobbing foundries with small quantities for which automated cleaning or press punching is not profitable at all. Considering increasing energy costs, which means EURO / kg melting, each kilogram of unnecessary melting should be avoided.

Read more: Low-pressure casting - an economic process (PDF, 2 MB)