It may seem that holes and windows are an oversimplified topic to discuss as far as design geometry is concerned. But when considering the effect on molten metal flow through the part it becomes clear that hole and window feature configurations play an important role in the manufacturability and final quality of a die cast part.
Holes and windows may also have an effect on ejection of the part from the die as the perimeter of these features will grip onto the die steel during solidification. To counteract this gripping action, generous draft should be added to hole and window features. The draft calculation for holes is covered in the Draft: Advanced Information module and may be used to determine the proper draft for holes and windows. When performing the draft calculations it will be noticed that hole and window features require more draft than any other die cast feature.
Molten metal flow may be blocked by through holes and windows. However, with the addition of bridge like cross feeders, overflows and flash-overs to the die casting die, the flow across through windows and holes can be re-established.