Subtract vs. Create with sheet bodies

[bbylls]

NX 8.5
Working in the rubber mold industry.
Is it better to just simply subtract the piece part model to create a cavity, or create the cavity by extracting sheet bodies from the part model and create other sheets to form a cavity block?
I've seen it done both ways, but don't know if either one is more beneficial than the other.

 

[ewh]

From an aerospace composites perspective...
Depends on the part.
If the molded part is solid, then subracting it directly from the mold body (after allowing for thermal expansion if that is a concern) is probably the simplist way.
For parts that are layed up as opposed to injected, I extract the mold surfaces from the piece part, add any surface extensions that may be needed, apply the CTE factor, trim the mold body to the resultant surface, then add any other features to the mold as required. A bit more involved, but as long as associativity is maintained the mold model will remain robust.

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