Quote Originally Posted by JAZZCNC View Post
This is why so meny build there own machines, DIY is about the only way you'll get near a correctly built machine with a similiar spec for around the same money, even then it will be close call sub £1500 if you want all the trimmings like 4th Axis.!
That's what I was about to say. The only way is to either do the research and DIY, or give someone who knows what they're a clear specification and get them to design and make it for you. I think DIY is the best option as in making the machine you'll learn more about how it behaves and what to look out for.

Quote Originally Posted by m.marino View Post
Down sides is that it requires very accurate cutting (but that is a common to all materials); it is required to be coated with something to stop oxidation from getting a start;
Cutting accuracy depends on how you're joining it. If it's just welded then you can make sure it's clamped accurately and rigidly whilst you weld and small gaps can be filled. For my frame I started off milling all the ends nice and square and milling a chamfer on. Then when I started welding it I realised it's a bit of a waste of time so I just cut it with my metal bandsaw (same as Jazz's), which at the time was cutting quite square and nipped the burrs off. Either way it helps a lot to have a milling machine and metal bandsaw. Frame cost me about the same as steppers and drivers.