After observing different users, it is found that users of mechanical pencils usually face different usage scenarios: ordinary writing or painting. The writing habits of users are also different in different usage scenarios. For example, users usually use the action of "throwing lead" when drawing and drafting line drafts, and hope to have a low center of gravity comfort when writing daily. Therefore, the function of automatically adjusting the length of the pen tip is added during the design, and the user can freely adjust the length during use.