Welcome to the place Dale! I'm currently coming to an end with my very first self design and build cnc. My main issue was using steel when i could of used aluminium and made my life much easier, I also used linear guide rails (1605 rails) which If i was to make another I would use linear rail slides purely based on they are have a better mounting system and carriages. Design wise there is quite a lot, there is the fixed base where the gantry will move over the work piece and there is also the fixed gantry where as the work will feed into the cutter.

This post here if you haven't already read it is one amazing read! Just simply amazing to see.
http://www.mycncuk.com/threads/10658...ue-welcomed%21

Rob