High Pressure Die Casting

For many years, high pressure die casting has been a proven and tested process in the industrial mass or series production of structural parts out of aluminum and magnesium for various applications. For several decades, vacuum has been used in the die casting industry to avoid air inclusions in the castings resulting in increased mechanical properties. To support the trend of more lightweight die-casted aluminum, we developed a multistage vacuum process called the Vacu2.

Application requirements

  • Fast pump down to 50 mbar
  • Process safety
  • Process monitoring

How does it work?
In die casting, a liquefied material – the so-called "melt" – is pressed into a mold cavity where it then solidifies. The purpose of vacuum in a die casting system is to evacuate a given volume of air from the shot sleeve and mold cavity within the shortest possible period. This avoids air inclusions in the castings. With the Vacu2 we have two stages and a direct connection to the shot sleeve and a connection to the venting valves. With this new multistage process, two mutually independent but coordinated vacuum stages are created. In the first stage, a vacuum vessel is connected to the mold cavity via the shot sleeve. After the plunger has reached the evacuation hole on the shot sleeve, the second vacuum stage is initiated. For this purpose, another vacuum vessel is connected to the mold cavity via the venting valves. Then, through a powerful pump combination, which has been tailored specifically to the vacuum die casting process, both vacuum vessels are put back exactly to the adjustable initial vacuum values to ensure the same starting conditions for each shot.

Schematic diagram of a variant of the multi-stage vacuum process

Leak detection
Often the press forms are water-cooled. It must be avoided that the cooling water used does not penetrate from the cooling channels inside the form to the melt side of the form. This would lead minimum to grain boundaries between various melt zones and to massive oxidation in case of stronger penetration. Regular leak detection from the cooling side to the melt side can guarantee trouble-free die casting and minimize loss of product. In both preventive press form control and troubleshooting, the cooling water side is emptied and pressurized with tracer gas (diluted Helium or Hydrogen / forming gas). On the melt side a localizing or global sniffing leak test is executed. This leak test can be applied for press forms used for metal and plastic production.

Product portfolio
With our Vacu2 system we can evacuate both the shot sleeve and the mold cavity and prevent air pockets in the die cast process, which translates to superior component quality. The Vacu2 eliminates the disadvantages of existing processes in terms of vacuum reached, process safety and process control. Furthermore time and expense required for mold building can be reduced since the process is less susceptible to leakage and conductivity. Pfeiffer Vacuum offers leak detection solution for the die casting industry.

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