general cnc with ramp 1.4

hello everyone

I'm have an old 3d printer that I want to convert to a more general purpose cnc machine.
what I mean is, I would like to have control of the machine so that I will be able to control the X, Y and Z axis with somekind of potentiometer or an rotary encoder.
I would also want the ability to move the machine tool to a certain coordinate with a GUI (maybe after I master the control with the potentiometer).
As of now, I've got an arduino mega with the ramp 1.4 shield.
there are 4 stepper motor ( 1 for x, 2 for y and 1 for z) and an limit switch (inductive sensor) for each axis.

The ultimate goal is to repurpose the machine for students projects in mechanical engineering college, so they could use this machine for all kind of ideas from pick and place robot to a self changing tool robot for different applications.

Can someone help in this issue? is there a software that can manage this application? I tried using he merlin software but I could'nt understand how to make it work.

Thanks in advance

You might consider the GRBL program which is used for general purpose CNC. I believe it normally works with a GRBL shield so I don't know if it can be configured to use a RAMPS shield - my guess is that it can be.