Hello again dear Ceyhan
First of all, thank you very much for the comprehensive and useful explanation. Based on what you said to ensure the intersection, I also tried the shaft with a larger radius, but the result did not change. Moreover, I tried to connect the blade and shaft through the "boolean operation union" and that operation also failed. In addition, my modeling method is to design the two blades separately and then reduced the vector domain "v" to [0,0.95] via the image surface. In the end, the "fillet surface" was used to connect the two blades, and your guess was correct. The reason for this is to create a softer connection at the tip intersection between the two blades. Please help me again and explain more about how to extend if possible.
Thanks.