"reinventing the wheel"
this is a common idiom meaning, working through the steps to re-engineer something that has already been done well.
from the Wikipedia
To reinvent the wheel is to duplicate a basic method that has already previously been created or optimized by others.
The inspiration for this idiomatic metaphor lies in the fact that the wheel is the archetype of human ingenuity, both by virtue of the added power and flexibility it affords its users, and also in the ancient origins which allow it to underlie much, if not all, of modern technology. As it has already been invented, and is not considered to have any operational flaws, an attempt to reinvent it would be pointless and add no value to the object, and would be a waste of time, diverting the investigator's resources from possibly more worthy goals.
The phrase is sometimes used without derision, when a person's activities might be perceived as merely reinventing the wheel, when they actually possess additional value. For example, "reinventing the wheel" is an important tool in the instruction of complex ideas. Rather than providing students simply with a list of known facts and techniques and expecting them to incorporate these ideas perfectly and rapidly, the instructor instead will build up the material anew, leaving the student to work out those key steps which embody the reasoning characteristic of the field.