paulwece:
I really really hope I don't have to design and build everything from scratch, but I need it to be of a certain size (x and y limit) because I need to fit it over something. Can't be too big or too small.
Don't you think it would help to tell us your size limits?
Also important is the acceptable range of positioning error due to mechanical "slop". You need to specify that as +/- N mm.
And that will also depend on the forces involved. Achieving high accuracy on a 3D printer is very different from on a metal cutting lathe.
You will get much better information if you tell us all about the project you want to create.
...R