To "reinvent the wheel" is to take great pains to devise another method to do something when a simpler method already existed.

You usually say this as a criticism. For example: "there is no need to reinvent the wheel!" - meaning "why don't you go forward with the problem, not go back and do things that are already understood, waste time..

from WKPD To reinvent the wheel is to duplicate a basic method that has already previously been created or optimized by others.