Re: cnc knee mill gearing
Every BP type CNC knee mill that I have seen either uses a 0.200'' or 5mm ballscrew. I can think of no reason to use a 10mm ballscrew. I'm not sure what your value of 7500 is, mm/min?
My machine has 750W, 3000 RPM servos, 2:1 reduction, and can hit 300 IPM rapids, but at 200 IPM it is physically unstable and frightening, and I limit the rapids to 100 IPM on the XY, and 30 IPM on the quill. I could bolt the machine to the floor and use higher rapid speeds, but I haven't found a good reason to do that. With a 32x14 work envelope, it doesn't take very long to rapid the full travel at 100 IPM and I'm not in that big of a hurry. For most work, the rapid moves are short anyway. If I'm in a hurry, I use my Haas with 400 IPM rapids. The BP clone is not a production machine, the Haas is.
Jim Dawson
Sandy, Oregon, USA