Back Charl so I'll answer here rather than email.!

Quote Originally Posted by Chaz View Post
How 'strong' is this DC setup? If FSWizard indicates I only need 0.5 HP (For example), surely the DC spindle should be able to manage? Could there be a setup problem with the DC drive (ie, just not setup correctly)? The fact that it is blowing 10A fuses implies its taking full power. On Saturday I had the spindle start to act odd, I need to see why but it runs and blows the fuse now when I power my mill (even before I ask for a spindle run).
It's only a guide so wouldn't pay too much attention has even same grade of materials can cut different from batch to batch.
check out the controller setup and wiring first if blowing fuses. Often blowing fuses for no obvious reason is a sign somethings on it's way out.!!

Quote Originally Posted by Chaz View Post
Do I replace the Sprint controller with a modern isolated version for £170ish excluding VAT?
No I wouldn't do that I'd look at alternatives.?

Quote Originally Posted by Chaz View Post
Do I spend £470 on a 4KW liquid cooled Chinese spindle with suitable VFD? Are they really able to deliver 4KW? From what I can see, I can probably cut a new plate (if I can get my spindle working properly) and get a 10 tooth gear onto the motor. The current gearing is 18 / 18 tooth. So this will take me to a max speed of 13300 RPM which will be good however I dont know if the system will have enough torque.
But not this alternative.? . . . It's more of routing spindle with high speed and low -ish torque and only at the rated speed is torque any good which is too fast.
Also you have to bare in mind the Spindle bearings and there speed rating. If Max speed was 4000rpm then I very much doubt the Spindle bearings will be rated for 13000rpm.!!

I'd look to replace the DC motor with AC asyncronous Motor like this one but the correct size for your needs which is the correct tool for the job.!
http://www.alibaba.com/product-detai...57.35.1.xZ2e8p