I have a small aluminium framed machine that was previously using a small 200 watt spindle. I changed to a 1.5kw spindle and after a few weeks its started making a rough noise on the Z axis. Thing is, is if I increase the speed/acceleration it sounds normal and like the spindle is no issue for it but I'm worried it will kill another driver chip(when doing 3d work) like a I did a few weeks back. Would springs on the Z axis rails help(pushing back against the Z axis) alleviate the weight problem. If I use my hand to lift the spindle a touch they sound returns to normal.

Thanks, any idea would be great!

Isaac