that is a heavy question.
I guess it depends on how close to the original each copy is
Most "new" ideas are based on concepts we have seen before.
As an example say you were making a Black Forest Cuckoo clock
There have been lots of designs made before, many look alike. If you were to copy an entire clock and change the character on thr front from a deer to a woodsman, I would say that was an infringement of the original copyright.
If you took elements from several clocks and made a new design, you could call it your own.
But thats just my opinion. I havent been in trouble with the law yet

This is certainly a very hot topic here. I am sure you will get lots of opinions.