im planning to buy a VMC for my machine shop mainly for making moulds. can anybody help me how to choose a right machine...what kind of tests must be done in the machine?.. im also interested to know about MB test piece...any body have a model file for this test piece?...

I am not a machinist, I am an engineer, but this is what I have done. First thing is to figure what will you use the machine for and what the travels should be.

What materials will you be cutting, steel, Pre-hard steel, graphite, Aluminum? What operations will you perform in this machine, Plate work, cavity and core geometry? You need to select the spindle RPM and drive HP based on your answers above.

Personally I was researching High Speed Machining and Hard Milling. I chose a current production part design that was originally produced by EDM. There was small detail that required .020" diameter cutter 1.25" deep in the cavity and by the way I was cutting pre-hardened H-13 50Rc.

The spindle is were it's at. You need thermal stability and rigidity. An easy way to check rigidity is to cut a .5" wide half round standing protrusion (like a pipe laying on its side)with the tooling path going up and over and back. The load on the tool and spindle changes as you go side to side, the effect will be tool chatter at the apex. Try this cut with the machine cold and again with it warm to see the change from thermal expansion in the spindle.

I wouldn't worry about the MB test, rather test the machine for your toughest application. Hope this helps.

thank u

nathan