combine feature (substract) / mold help

[slow_rider]

i'm desiging a simple mold for a silicon part, the mold will be a two part mold with a base that has a cavity and a cover that will close the mold.

i designed the rubber part and i wanted to use the combine feature to substract the part from a block i draw around it. the problem is that when i do that, combine is gray and can't be used. when i draw the block near the rubber part (without them touching) i can use the combine feature but off course it is not useful this way.

the rubber part is made out of around 50 features. could that be the reason i can't use combine? does it need only single features? like two extruded boides but nothing more complex?

how can i substract the complex part from a block of material?
thanks!

 

[justin22885]

why dont you try combining all those smaller features of the rubber piece into one? and try it that way? or when you select the rubber object, try selecting it from the feature manager design tree instead of clicking on it