Part placement program? to maximize use of space?

Anyone know of a cad program to maximize the use of a given space, in
regards to part placement?



I want to put some parts onto aluminium, but trying to minimize waste as
well.



Program needs to have the following attributes:

- a minimum distance away another part

- [optional] able to give an odd shape source material to cut from.
[i.e. instead of virgin stock, stock that already has a chunk out of it.



Thanks.



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