CPT International 04/2014


The leading technical journal for the
global foundry industry – Das führende Fachmagazin für die
weltweite Gießerei-Industrie


Figure 14: Vacural process

Figure 15: Process vacuum vs. Vacural

Figure 16: Safety parts (Source: Brabant Ritter, Germany)

is, a higher density of components and

thus better mechanical properties.

The resistance-heated heating of

the casting system (Figure 12) is standard

in zinc diecasting for many years.

Now this technology is also available

for the more challenging temperature

range of magnesium hot chamber

machines, which contributes to

improved reproducibility in the process.

It is now possible, to adjust and control

the temperature profile along the

gooseneck nozzle system accurate to a

few degrees. The slim design allows for

immersion into the dies, so that magnesium

die casting can take advantage

of the benefits of a shorter sprue area.

This heating also allows to use reproducible

different modes of casting. A

few degrees at the nozzle tip temperature

allow a magnesium casting with or

without plug or even a melt down, as

the founders know so far from the zinc

die casting (Figure 13).

In the cold chamber die casting vacuum,

techniques are used for highly

stressed structural parts, respectively,

weldable aluminum die casting

parts. The classical vacuum systems

on conventional cold chamber die

casting machines struggle with the

rapid venting immediately after dosing.

Evacuating usually extends thereby

the residence time of the melt in

the relatively cold sleeve. The machine

manufacturers try to counteract

effects such as peripheral shell

hardening, etc., with a higher melting

temperature. Although very veritable

results are achieved, the Vacural

die casting (Figure 14) opens up completely

different possibilities.

Here in the Vacural process the evacuation

of the die starts before dosing.

Moreover, the machine now doses via

a special suction device directly from

an aluminium holding furnace into

the shot sleeve. Is the desired vacuum

reached, the casting quantity is also

dosed and the machine can cast the

part without major retention of the

melt in the sleeve.

The process of Vacural die casting is

self-monitoring. Leaks in the die, which

do not allow to achieve the desired vaccum,

inevitably lead to a faulty dose

of metal. So the machine can detect by

measuring the piston stroke, that this

part has not the desired quality, with

respect to microporosity. Without further

testing and without additional

sensors a process and quality control is

thus ensured. Vacuum die casting with

classical die casting machines can not

perform this (Figure 15).

Heat-treated safety components

for the automobile industry can be

manu factured with the Vacural process,

among other things. These include

suspension parts (Figure 16) that

20 Casting Plant & Technology 4/2014

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