Is it possible to make a good SOLID machine using extrusion? I have read mixed points of view about this stuff...Some say its really ideal for upgrading a machine in the future and provides a good solid frame while other say that its rigidity could be called into question.

I am able to get easy access to a welding machine and welder(friend) but would rather not go down that route( Cutting steel,jiging, powdercoating etc) If i can make a CNC from extrusion..that would be ideal. Though I wouldnt mind making the gantry out of thick steel screwed into the linear blocks. That wouldnt be a problem.