Dear Hamed Aghababaei , the mold should be the complimentary 3D object of the object you want to obtain. If you are using some 3D software, such as CAD you could design your cylinder with the closed end and another 3D volume larger than your cylinder (it could be another solid cylinder or a cube for example). Then you can substract your closed end cylinder from the solid volume with a boolean operation. The result 3D object would be your mold. Once you have the 3D file of your mold you could fabricate it by machining (turning) in the appropriate material (steel, brass...) to withstand the applied pressure.

If you already has a real cylinder with a closed end as the one shown in the pictures, then you could use it to make the mold. Again you starts with a solid piece of material, say a cylinder, you should remove a cylinder with a thickness equal to the thickness of your desired cylinder and the deepth equal to the high of your cylinder. Then you must machine the upper part of the inner cylinder of your mold, to define the closed end.

Here you can see a 2D projection of this process: File name: Mold1.jpg

Alternatively you could start with a solid cylinder, turning a cylindrical hole with diameter equal to the external diameter of your own cylinder and depth equal to the heigth of your cylinder. In a second step you start with another solid cylinder and turn it till achieving a diameter equal to the internal diameter of your cylinder and the length equal to the depth of your cylinder, leaving a cap to hold this cylinder and that allow to center it with the former one as shown in the following image: File name : Mold2.jpg.

You also could build a mold with the desired shape inside, and to open it the block can be cut through a longitudinal plane in two halves.

Hope this helps. Good luck with your research and best wishes.