How to create mold from complex part?
The part is 3D scanned and I have a problem with creation of mold (core and cavity)
The first this you may want to try is adding split lines to clearly define a parting line. Numerous faces appear to straddle a possible parting line. Another possible issue is that there seems to be an undercut or pocket on one of the surface that would require a side action to allow the part to be removed from the mold. This face may need to be modified to allow removal from the mold without adding side action tooling.
The parting line for the inner opening needs to be better defined. There is an undercut that is preventing a clean parting line from being created by the software. The ends of the curve for the inner parting line don't meet without passing over the surface of the undercut. See the attached image. The surface highlighted in blue shows the undercut on the upper right side of the inner opening.
Depending on the volume of parts you're looking to have made, two low volume alternatives that wouldn't require changes to the model would be investment (lost wax) casting, or urethane mold casting. Both methods would allow for undercuts and imperfect surfaces that other methods would not tolerate.
I can try this part by spiliting it in to Core and Cavity. For these type of part you should set the viewing direction first means, First decided the Ejection direction and from ejection direction split it in to parting line by silhouette curves method.