在通风除尘管道的制造中常用的异形接头，其加工制造一般是先在金属薄板上画出展开图，然后落料加工成型。画展开图一般采用三角形法，这种方法在操作上较为繁琐，本人在实践中探索了一种简单展开法，作图简便准确，现介绍如下。天圆地方是异形接头中最常见的一种，在此以图１ Commonly used in the manufacture of ventilation dust pipe shaped joints, the processing and manufacturing is generally drawn on the metal sheet unrolled plans, and then blanking forming. Drawings generally use the triangle method, this method is more cumbersome in operation, I explored in practice a simple method of expansion, simple and accurate drawing, are presented below. Round the world is the most common type of connector, here in Figure 1