[Scott_bob]

I am thoughly enjoying this discussion...

This is really crucial for the Fanuc and apparantly the Mazak guys to fully understand. And for those poor souls who still have Fadal controls well, they cannot understand what you are talking about when you say your CNC is silky smooth at "programmed" feed rates of 400 - 500 Ipm.

Also, it is crucial for CNC users to understand that without buying those expensive options that your machine tool builder is selling, you cannot understand what is being said above, any more than the Fadal users (who don't have these capabilities). Without these upgrades to your Fanuc or apparantly Mazak controlled CNC cannot perform at these high "programmed" feed rates...

This is a fact. Evidence: see above...

I also share the frustration "above" that it is too much trial and error to get both accuracy and high performance feed rates out of a Fanuc.

I have witnessed, and handled with my own hands, and trained others to use this control called the Numeryx. I have never seen better motion control. If you have a passion for your machining, go see one in action.
They are out there. If you want 2nd to none performance, why not take a trip. Go to Detroit yourself, or one of the high speed machining shows and get a demo of this control.

By the way, the feed rates you mention above where possible on the Fadal we retrofitted with the Numeryx and the ballscrew thrust bearings saw less jerking than they did with the Fadal MP32. This machine could hold accuracy of +/-.001 at very high feed rates as long as you have already taken care of tool deflection by leaving .005 or .010 for the finish pass. As long as you are climb milling your deflection will be away from your 2D feature, and in 3D there are no undershoots or overshoots to worry about. It's all automatic, no G61.1 or G5 or any other modifers either. It's just accurate all the time. Set one high feed rate your tool can handle, don't cut too deep for that tool and let it go. This is no exageration...

Good discussion on this subject!