This defect is often present in casted parts. In these areas the molten metal reaches a limit value of solid fraction. We’re talking about 30% (blue color), over this value the flow stops leaving unfilled zones. Even over the 10% (yellow color) the metal flow slow down and the result is the presence of ripples on the surface. Those defects are present in the areas that fill at last and are amplified by excessive cooling of the melt due to excessive cooling of the mold or too long filling time and also if the wall to fill is too thin.
