Cutting conditions mill spindle rpm limit - help needed

[fandango]

Hi can anybody help, i am trying to adjust the cutting conditions on the integrex's in our shop so that when using the autoset feature whilst programming in mazatrol the surface speed / feed rate etc are correct for the various material types we have added. The machines are integrex 400y's with fusion 640mt controllers.
The problem i am having is that the autoset will only set a surface speed / velocity for the tool that will result in the mill spindle reaching a maximum 3000 rpm as opposed to the 6000 rpm the machines are capable of.
An example of the problem is- I want to set the cutting conditions to auto set a U-Drill at a velocity of 160m/min, in a steel we reguarly cut at work. If i program for example a 30mm U-Drill it will auto set at 160m/min, and if the drill size is larger, it will keep auto setting to 160m/min, BUT as the size comes down, thus requiring it to eventually exceed 3000rpm, it will then auto set a velocity lower than 160m/min to keep it at 3000rpm. This is the same for all operations using the mill spindle. I can manually enter a velocity myself and the machine will exceed 3000 rpm no problem at all right up to the 6000 rpm maximum.
I have spoken to both applications and service engineers at mazak about this but they dont seem to be able to come up with why the control is limiting the mill spindle rpm in this way. It is my guess that this as with most things mazak is a parameter issue which the engineers in the uk may not be familiar with as the integrex is a japanese built machine.
I would be interested to know if anybody else here has noticed this problem or even better if they may be aware of how to get the control to autoset upto the machines full capability.