A restricted flow mystery

摘要

An undersized sprue is a common source of trouble,but not always,as demonstrated with the following defective part.I received a package that contained just the sprue,runners,and a small section of the part in which the sprue,runners,and gates were located.The note said the part was a large,double-sided piece that looked like two boat trailer fenders joined together by the gate area.The material was an 8-melt copolymer polypropylene that was colored by the molder at the machine using a color concentrate blender.