The question was building a self built machine.
The answer is.. Yes it can be done. There are self built cnc machines that are just as capable with professional quality plug and play controllers using hardware easily available to anyone.
One person can build a cnc out of a hardware store. They are not all that complicated.
There are designs around that outperform a cheap Chinese built. Outperform means Fast, accurate and stable enough to cut with accuracy.
There are self built cnc forums all over the net where any body can get guidance to build a reasonable cnc machine that will operate on most materials (excluding ferous metals) used in
sign making for about 7 grand.