ready for 3d printing. solid model.
Also if you want to model by yourself you can watch Nishant Gautam's videos.Thanks for him to share videos. https://www.youtube.com/channel/UCsD2zKOCUtw5oVSkx2FOv9Q
I enlarged the inside of the second STL version uniformly. The surfaces now meet each other, closing the gap between them. This way, obtaining the output without using supports will be easier.
second version name is: scaled_innerpart.