In the diecasting of Zinc Alloys, it is possible to get many advantages with a correct evacuation of the gas present in the mold, in the siphon, and in the extension. The first advantage is an important reduction of the porosity and increased cast quality from both a structural and aesthetic point of view.
In particular, the gas evacuation is important for the production of the components which require post-production processing, such as painting, galvanic treatments, and plastic cases.
The application of the vacuum technology in hot chamber diecasting must consider some critical issues with which to characterize this process:
- The air volume which has to be evacuated is from 5 to 40 times the volume of the component (in cold chamber 2 or 3 times).
- The process is extremely fast (the filling time for a decorative component is max 20 msec) and speed over 50 m/s can generate turbulence, vortex, and subsequent air presence.
- The temperature range between liquid and solid is very small (6-8 degree range, while the aluminum has a 50-70 degree range). This means that if there is gas trapped inside the metal it cannot be eliminated anymore.
- In high aesthetic quality components, which undergo galvanic treatments, even micro porosity with small volume (ex. 1% of the volume of the piece) can become surface defects which cause disconformity.
- The components can be really small and light, and subsequently also the mold has a small size. The application of a vacuum valve can cause problems for its excessive volume.
Fondvacuum® offers its integrated system which eliminate the critical issues:
- High capacity and reliability pump with customizable vacuum level in the tank.
- Possibility of programming the vacuum regulation (pre-vacuum) to avoid cavitation and excessive turbulence, caused by absence of air counter-pressure.
- The gas evacuation is very fast and precise, with a control which guarantee maximum reliability. The fast-working valve closes at the end of the filling phase, to ensure the evacuation of all gas pushed by the liquid metal. The fast-working valve has been built with extreme precision, to guarantee a closing time of 1 msec.
- The ratio between valves volume and suctioning capability is optimal, the Fondvacuum® system is convenient also for small casting sites and small molds.