Wind whistle
Windpipe (also air whistle or draft hole ) describes a channel in a casting mold through which air, hot gases and slag displaced during casting can freely escape upwards so that the mold can be completely filled. In addition, windpipes serve as a reservoir ( feeder ), from which material can possibly sag during solidification and additional pressure is exerted on the casting compound. The unwanted "appendages" of the casting caused by whistles, like the pouring funnel and seams, must be removed by further processing after demolding .