Since you mentioned PCB routing, this is a planset for a machine specifically designed to route PCBs.
http://www.crankorgan.com/brute.htm
Sorry about linking to *his* site, guys...but it's a perfect answer for his question. This machine is designed around routing PC boards...it's simple to build, and according to all reports it works quite well. In fact, many of us who are homebuilders were directly inspired by one or more of *his* ideas and designs.
Show the pictures of these machines to your dad, and realize that this one makes extensive use of extruded aluminum window channel. It's "commonly" available in the USA...not sure if you have something similar in your country. It's a large extrusion (4x6" in cross section, for the extrusions I have in the garage) in the shape of the letter C...lets you use simple parts to slide around on the extrusion. The sliding parts are plastic, and fit *around* the edges of the extrusion. Viewed end on they resemble a letter H.
That should be enough of a hint for you, without giving away all of his secrets...
Like I said earlier -- don't be afraid to get creative. There is a wealth of information and expertise on this site, and we're all VERY willing to share it.
Seriously, though, here's some free advise -- build a simple and small machine first. You can reuse the expensive parts like the motors and circuitry on machine #2, and use the smaller machine to build the precision parts for the bigger machine. Your biggest enemy will be flex...and it's easier to keep small machines from flexing.
-- Chuck Knight