The MechMate has a steel right angle sitting on top of a "C" channel. The right angle rail's vertical edge has an inverted V edge ground into it. V shaped ball bearings roll along the edge of the rail. Anything that falls on the V edge will either fall off of it or will get squeezed off when the V bearings roll over it. The MechMate gantry is 250+ pounds. Two of my local friends built a 5' x 10' version and it is a smooth working system.
A good dust collector and dust shoe will keep the machine very clean. If the project can't be cut with a dust shoe in the way then you will stay busy vacuuming the machine as it works.
CarveOne
CarveOne
http://www.carveonecncwoodcraft.com