The reason and prevention of four kinds defects including surface wrinkled skin (carbon built-up), chock, blow hole, deformation, was introduced in this part of the article.
本部分主要介绍表面皱皮（积碳）、呛火、气孔、尺寸超差及变形等缺陷的产生原因和防止方法。
2
A lot of lab study and test have been done to the problems of bad reliability and short life-span for traditional slip-type down holechock.