Don't let your Overflows ruin your Casting

In the last few years, I have seen more and more that the overflow system determines the casting quality. That sounds strange, as the overflow fills after the casting. So, as long as the vacuum system can suck enough air out of the mould, it does its job. Add some beans to give the possibility to push metal meetings out the casting the job is done for the overflow system.

Where is the issue, then?

Most of the overflow systems are copy-paste solutions from previous parts. These parts are designed with an AlSi9Cu3Fe or an AlSi10MnMg in mind, and they work perfectly.

The issue comes with the usage of low-silicon alloys. A simulation engineer only looks at the overflows if there is a problem within the part. By surprise, the overflows stick to the die as soon as the first casting trial starts.

Low silicon alloys are more sensitive to high metal speeds. They stick to the mould quite quickly. To prevent sticking, the casting parameters must be adjusted to reduce the speed in the overflows. This compromise usually means lower casting speeds and/or early break usage. The result is often a lower-quality casting and no one wants that! So, please check your overflow metal speeds in the simulation!

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