You --->
<----CNC machine designed this way...lol
just kidding with you, but seriously you will need to keep reading in this benchtop forum to get better ideas, this design is seriously unrigid/flawed for the purpose you stated or any type of cnc machining other than maybe styrofoam...
what kind of budget are you working with? that is a good starting point for advice now that we know what you will be cutting, also what is the size of the largest part you need to cut?
I think you may find it is cheaper to buy your first machine rather than build it....(im talking about the actual machine itself, not the electronics)