I have a little backlash in all axes of my fadal 4020, trying to improve this a little if possible. I had the way covers off yesterday to fix an oil line and i noticed if i try and twist the X ballscrew with my hand you could easily see the coupling flexing without much force. Servo end was staying put while the rubber spider was flexing. Is this normal or are my coupling worn? Or is it just poor design to start with? My couplings have 3 lobes, i only see 2 lobe and 4 lobe for sale as replacements. Would these be any better? Would a new spider work for mine?
Any suggestions on determining how much backlash is from coupling and how much is from ballscrew? Thrust bearings appear good on the X axis. Tried indicating the groove of ballscrew from table to check ballscrew but i have over 0.001 runout in screw so its hard to say.