Take "z-yz" as the datum level and position from the bottom, 45mm in height and 70mm in length. Draw a circle with a diameter of 20 and 40 mm, starting from -10 mm and ending at 10 mm, as shown in section 2.18. Draw a circle with a radius of 40 and 50 mm on a flat face as the center of the circle to form a closed curved surface. As shown in the figure, the stretch length is 25 mm2.19 strips, and then the Boolean operation is performed to trim the body to obtain a figure of 2.20 strips.