Hi Mike,
whether you use ordinary steppers, closed loop steppers or servos is not that important, any of these devices can do the job.
If ger21 is correct that your lead screws are 1/4 diameter then the speed at which you can rotate them before resonance is limited,
additionally they will flex torsionally for a loss of accuracy and if you up the torque the problem gets worse.
Look at your machine and see if you cant replace those lead screws with, ideally ground ball screws (really really expensive),or
rolled screws. Ebay has zillions of them, go for 16mm ones if you can get them to fit. They typically have a pitch of 4,5 or 6mm
so to spin them at 1000 rpm means rapids of 4m, 5m or 6m per minute, very useful.
If it proves impossible to replace your existing lead screws then significantly increasing the speed of your machine will be limited.
Under those circumstances better specified but otherwise standard steppers with decent drivers and a 68V+ power supply would easily
provide an increase in speed up to the resonance limit of the machine whilst conserving you budget. You could certainly achieve similar
results with servos say, they would cost a lot more and you will still only be able to turn up the wick to the limit imposed by the
mechanics of your machine not the capability of the servos.
Craig
Thanks very much for the information. Yes, I never intended to go full bore with the servos because of the limitations of the machine. I only wanted to be able to have quiet motors that can swiftly do rapids (within limitations of the machine of course) without loosing steps. I think after all the input from everyone, steppers are going to be the best option in this case. I guess I will just have to endure the "wrrreeeeerrrr" noise and settle for steppers. I really don't want to go so far as to replace ball screws. Id would then consider a different machine in that case which already has ball screws like the X2 or something like that. it was my thinking that if I am going to spend close to a grand in new steppers, driver boards, and a BOB, it was worth looking into servos for a bit more money and take advantage of more speed and quiet operation. Apparently the design of my machine simply will not allow any justifiable benefit from using servos. So I have decided to do nothing and just keep my mill the way it is. For everyone who was patient enough to put up with me, I really appreciate the knowledge that was shared.