Base structure of cooling fan and manufacturing method thereof

A manufacturing method of a base structure of a cooling fan, the manufacturing method comprising steps of:

• providing a bearing defining therein a first cylindrical cavity;
• inserting a shaft of the cooling fan into the first cylindrical cavity;
• providing a shaft sleeve made of a first material and defining therein a second cylindrical cavity having a first opening and a second opening at a first end and a second end of the shaft sleeve, respectively, the shaft sleeve having:
• a protrusion part arranged at the first end of the shaft sleeve and protruding from an inner surface of the shaft sleeve toward the second cylindrical cavity;
• and
• a first engagement structure provided at the second end of the shaft sleeve;
• inserting the bearing into the shaft sleeve through the second opening till reaching the protrusion part;
• putting the shaft sleeve in a mold to make the first engagement structure of the shaft sleeve located in an accommodation room defined in the mold;
• and
• performing an injection molding process to form a base having a second engagement structure by injecting a second material into the mold, wherein the second engagement structure is interlocked with the first engagement structure since the second engagement structure is integrally formed with the base in the injection molding process, thereby restricting the shaft sleeve from moving with respect to the base.