Aluminium Pressure Die Casting Process Problems

Why do you need to cast such thick walls? Reconsider your design. A criss-cross web of thinner supports will support a thinner wall, reducing pororsity AND resulting in material and cost savings. If still more strength is required, consider casting in alloy steel reinforcing parts.

Also, reconsider the alloy you are using, some have higher shrink rates than others.

Is all your porosity due solely to shrinkage (creating pockets of vacuum porosity). You may also be experiencing air pocket porosity, or porosity caused by other gases. Good venting in your die design can help. Also, Vertical diecasting machines yield lower gaseous porosity than standard Horizontal types, as released gasses will bubble up through the melt, rather than being injected into the dies.