DIY projects

There are number of apps that can separate your stl. I use Blender and AdMeshGUI to break them apart personally.

You can use cutting tool support for that.

how?

I guess the first solution is to make improvement on the part molding. In a lot of cases you can do molding and cutting at the same time.

As a second solution, use a steel-rule cutting-die, they make circular punch dies as a standard size, it might match your diameter. You can make a full or a section cutting-die, and they are not expensive. If you buy the punches you can make it yourself by using a wood die board.

Can you share more 3D pictures about it?

I an sending you a sample, it may not work for what you want. The solution for your problem is in the molding, you must mold the part clean without the flash on the parting line. https://www.wagnerdiesupply.com/Images/Punches-Tech-Grp-2-2018.jpg

how to position correctly?

it is imperative to cut it all in one go

I recommend you make a sample of 4 cavities to test. As far as the "position" I am assuming you have the center-lines of the "position". Once you tested with the 4 cavity then you can proceed with all of the parts in one cut operation. Again, you must look at the molding of the parts, it seem you need a stronger press (more tonnage) to mold the parts.

Also, you mention to cut "correctly" you can make an individual floating cutting die, meaning, all parts are floating separately.